* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lipoteichoic Acid Synthesis and Function in Gram
Survey
Document related concepts
Oxidative phosphorylation wikipedia , lookup
Signal transduction wikipedia , lookup
Butyric acid wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Western blot wikipedia , lookup
Peptide synthesis wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Metalloprotein wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Lipid signaling wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Biochemistry wikipedia , lookup
Proteolysis wikipedia , lookup
Biosynthesis wikipedia , lookup
Transcript
MI68CH05-Grundling ARI V I E W A 15:26 Review in Advance first posted online on May 5, 2014. (Changes may still occur before final publication online and in print.) N I N C E S R E 26 April 2014 D V A Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. Lipoteichoic Acid Synthesis and Function in Gram-Positive Bacteria Matthew G. Percy and Angelika Gründling Section of Microbiology and MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ UK; email: [email protected], [email protected] Annu. Rev. Microbiol. 2014. 68:81–100 Keywords The Annual Review of Microbiology is online at micro.annualreviews.org bacterial cell wall, D-alanylation, glycosylation, cholination, lipid turnover, osmoregulated periplasmic glucans This article’s doi: 10.1146/annurev-micro-091213-112949 c 2014 by Annual Reviews. Copyright All rights reserved Abstract Lipoteichoic acid (LTA) is an important cell wall polymer found in grampositive bacteria. Although the exact role of LTA is unknown, mutants display significant growth and physiological defects. Additionally, modification of the LTA backbone structure can provide protection against cationic antimicrobial peptides. This review provides an overview of the different LTA types and their chemical structures and synthesis pathways. The occurrence and mechanisms of LTA modifications with D-alanyl, glycosyl, and phosphocholine residues will be discussed along with their functions. Similarities between the production of type I LTA and osmoregulated periplasmic glucans in gram-negative bacteria are highlighted, indicating that LTA should perhaps be compared to these polymers rather than lipopolysaccharide, as is presently the case. Lastly, current efforts to use LTAs as vaccine candidates, synthesis proteins as novel antimicrobial targets, and LTA mutant strains as improved probiotics are highlighted. 81 Changes may still occur before final publication online and in print MI68CH05-Grundling ARI 26 April 2014 15:26 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. Contents INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LTA STRUCTURES AND THEIR SYNTHESIS AND FUNCTION . . . . . . . . . . . . . Polyglycerolphosphate (Type I) LTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Type I LTA Synthesis and Lipid Turnover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complex LTA Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Streptococcus Pneumoniae (Type IV) LTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MODIFICATIONS OF LTAS AND THEIR FUNCTIONS . . . . . . . . . . . . . . . . . . . . . . . D-Alanylation of LTA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glycosylation of LTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phosphocholine Modification of Type IV LTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . APPLICATIONS OF LTA AND MUTANT STRAINS . . . . . . . . . . . . . . . . . . . . . . . . . . . COMPARISON OF TYPE I LTA AND OSMOREGULATED PERIPLASMIC GLUCAN SYNTHESIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 82 82 85 86 86 87 87 89 90 91 92 92 INTRODUCTION TA: teichoic acid GroP: glycerolphosphate RboP: ribitolphosphate WTA: wall teichoic acid LTA: lipoteichoic acid OPG: osmoregulated periplasmic glucans Teichoic acids (TAs) were first detected by Baddiley and coworkers in 1958 (6, 7). A structural diversity was soon recognized, and the term TA, derived from the Greek word teichos, for “wall,” was subsequently used to describe all bacterial cell wall, membrane, and capsular polymers containing glycerolphosphate (GroP) or ribitolphosphate (RboP) residues (8). Currently the term TA describes two bacterial cell wall polymers found in gram-positive bacteria: wall teichoic acid (WTA) and lipoteichoic acid (LTA). WTA synthesis has recently been reviewed (17), and here we focus only on LTA synthesis. LTA is now defined as an alditolphosphate-containing polymer that is linked via a lipid anchor to the membrane in gram-positive bacteria. However, this definition may need to be revised to include recently described complex glycosyl-phosphate-containing polymers (107). LTAs have been grouped into different types based on their chemical structures (Figure 1). This review focuses on the synthesis, modifications, and functions of type I and type IV LTAs, as these have been studied in the greatest detail. Furthermore, we summarize recent attempts to utilize LTAs as vaccine candidates, LTA mutant strains as improved probiotic strains, and biosynthetic enzymes as antimicrobial targets. Lastly, we highlight similarities between the synthesis pathways of LTA and osmoregulated periplasmic glucans (OPGs) of gram-negative bacteria. LTA STRUCTURES AND THEIR SYNTHESIS AND FUNCTION Polyglycerolphosphate (Type I) LTA Polyglycerolphosphate, or type I LTA, is the best-characterized LTA. It is found in a large range of gram-positive bacteria belonging to the phylum Firmicutes, such as Bacillus subtilis, Staphylococcus aureus, and Listeria monocytogenes. Type I LTA has an unbranched 1–3 linked GroP backbone −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−→ Figure 1 Different LTA types. Chemical structures of (a) type I LTA as found in Bacillus subtilis, (b) type II LTA from Lactococcus garvieae, (c) type III LTA from Clostridium innocuum, (d ) type IV LTA from Streptococcus pneumoniae, and (e) type V LTA from Clostridium difficile. Glycolipid anchors are shaded; R indicates a fatty acid, and R1 denotes backbone substitutions. 82 Percy · Gründling Changes may still occur before final publication online and in print MI68CH05-Grundling ARI 26 April 2014 15:26 a Type I LTA O HO OR1 O P O O– O OR1 P O O– O OR1 O P O O O– O HO HO OH b Type II LTA HO OH O O HO OH HO O HO HO O OH O Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. HO O O O O HO HO H3N+ R1= R O O OH OH O R O O HO HO H3C D-Ala AcHN GlcNAc O OH O HO OH O O P O– O HO O HO O OH HO OH O HO O HO O O OH O OH O P O O– HO HO O O HO O HO O O OH O R O c Type III LTA O P O O O– HO OR1 HO O O O OH O P O O O– HO OR1 HO O HO O OH OH O OH O O O R HO HO HO H3N+ O NH3 OH O R1= HO O R R O O AcHN GlcNAc Gln d Type IV LTA N+ N+ O– O P O O– O O P O O O O O HO O O O NHAc O NHAc HO N+ N+ OR1 OR1 OR1 O O– P O O HO HO H3 O N+ O OH O P O O O O– P O O O O OR1 O HO O O O NHAc OR1 O O OR1 NHAc NHAc O HO O– P O O– O O O HO H3N+ O O O H3N+ R1= H3 C e Type V LTA HO HO H3C O O R O NHAc OH HO HO R O OH O HO O O D-Ala O O P O NH O– HO O HO C O HO O O H C OH O 3 H3C NH NH C O HO O C O HO O H3C O O P O O– HO HO O O OH NH C O O HO O OH O HO HO O OH O O HO HO O O O R O OH www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print R O 83 O MI68CH05-Grundling ARI 26 April 2014 15:26 Polyglycerolphosphate chain Glc2-DAG 25x + DAG P LtaA LtaS PgsA P YpfP 2x UDP Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. OH OH OH O UDP OH ? P P CdsA CDP P DgkB P CMP GroP PPi CTP ADP ATP Figure 2 Type I LTA synthesis machinery and lipid turnover in Staphylococcus aureus. The glycolipid anchor Glc2 -DAG is produced by YpfP and moved to the outside of the membrane, likely by LtaA. The LtaS enzyme produces the polyglycerolphosphate chain by the repeated addition of GroP residues to the tip of the growing chain using the lipid phosphatidylglycerol (PG) as substrate. The concomitantly formed DAG is recycled in the cytoplasm to PG in reactions catalyzed by DgkB, CdsA, PgsA, and as of yet unknown enzyme(s) with phosphatidylglycerol phosphate phosphatase activity. The scissors indicate the processing step of LtaS by the type I signal peptidase SpsB. This figure was adapted with permission from Reichmann & Gründling (106). The publisher for this copyrighted material is John Wiley and Sons. Abbreviations: DAG, diacylglycerol; Glc2 , diglucosyl; GroP, glycerolphosphate; LTA, lipoteichoic acid. PG: phosphatidylglycerol DAG: diacylglycerol 84 structure and is usually linked to the bacterial membrane via a glycolipid anchor (33, 106). The hydroxyl groups at the C2 position of the GroP repeating units are, to varying degrees, modified with D-alanyl or glycosyl groups. The key enzymes involved in type I LTA synthesis have been identified and are depicted in Figure 2 for S. aureus. The glycolipid anchor is produced in the cytoplasm of the cell by the glycosyltransferase YpfP, which uses a nucleotide-activated sugar as substrate, and this lipid is then moved to the outside of the membrane, presumably by the flippase LtaA (43, 59, 60, 66). The GroP chain is then extended on the glycolipid anchor by the repeated addition of GroP subunits derived from the head group of the membrane lipid phosphatidylglycerol (PG) (69, 116) by the action of the LTA synthase (LtaS) enzyme (44). The crystal structures of the enzymatic domain of the LTA synthases YflE from B. subtilis and LtaS from S. aureus have been determined, including a cocrystal structure with GroP, providing insight into the binding of the lipid head group to the enzyme (77, 110). LtaS enzymes are processed between the membrane and the extracellular enzymatic domain, likely by type I signal peptidases (132). Whereas the soluble extracellular domain of LtaS can hydrolyze PG to diacylglycerol (DAG) in vitro (61, 108, 131), expression of this domain alone is insufficient for LTA synthesis (132): Only the full-length enzyme can produce LTA in vivo. A model has been proposed in which the signal peptidase–dependent cleavage of LtaS serves to inactivate the enzyme under conditions where LTA production is no longer required (132). Even though all type I LTAs contain the same GroP backbone, the number of LtaS-type enzymes involved in its synthesis differ between bacterial species. In S. aureus, LtaS initiates and extends the GroP chain, whereas in L. monocytogenes LtaP links the first GroP to the glycolipid anchor, after which LtaS extends the chain (44, 128). Many other bacteria contain multiple LtaS Percy · Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 enzymes; however, the two-enzyme system found in Listeria spp. appears to be unique, as LtaP has significantly diverged from the LtaS enzyme. In Bacillus spp., which contain four LTA synthase enzymes, these proteins are more closely related to each other and the LtaS protein of L. monocytogenes than to LtaP. Disaccharide-containing glycolipids are often the predominant glycolipids and are present both as free membrane lipids and as LTA anchors such as β-glycosyl(1–6)-β-glucosyl(1–3)diacylglycerol (Glc2 -DAG) in S. aureus and B. subtilis or α-galactosyl(1–2)-α-glucosyl(1–3)-DAG in L. monocytogenes (34, 59, 60, 66, 69, 123, 128). However, glycolipids with mono-, tri-, or tetrasaccharides are also found in bacterial membranes and are used as LTA anchors, and they can be further substituted with acyl chains or fatty acids (33). A growth temperature–dependent variation in the LTA lipid anchor has recently been observed for L. monocytogenes (28). The anchor contained a second DAG lipid when the bacteria were grown at 37◦ C, and this LTA polymer showed reduced binding to the eukaryotic pattern-recognition protein L-ficolin (28). A comprehensive review covering the diversity of glycolipids and phosphoglycolipids and their interrelationship with LTA synthesis was published some years ago but is still relevant (33). Enzymes involved in glycolipid synthesis were covered in a recent review and are not further discussed here (106). Mutations in ltaS have now been generated in S. aureus, B. subtilis, Bacillus anthracis, L. monocytogenes, and Lactobacillus acidophilus (39, 44, 91, 97, 110, 128, 131). With the exception of L. acidophilus, strains either lacking LTA or with defects in LTA backbone synthesis have severe growth defects. L. monocytogenes, B. subtilis, and B. anthracis ltaS mutants display a filamentation phenotype, which in B. subtilis was attributed to the inability of the key cell division protein FtsZ to assemble at the division site (39, 110, 128, 131). In addition, evidence of a direct interaction between cell division proteins and LTA synthesis proteins was recently provided for S. aureus (105). An S. aureus ltaS mutant can only be maintained under osmotically stabilizing conditions in medium with a high concentration of NaCl or sucrose, after acquisition of compensatory mutations, or, for some strains, by lowering the growth temperature (22, 44, 97). The observation that an S. aureus ltaS mutant can be rescued in high-osmolality medium or by an increase in the cellular concentration of cyclic-diadenosine-monophosphate (c-di-AMP), a nucleotidesignaling molecule that has been implicated in the control of potassium and/or other ion transport (9, 22–24, 94, 97), might indicate a crucial function of LTA in the osmoprotection of the cell. Type I LTA Synthesis and Lipid Turnover Type I LTA synthesis is intimately linked with lipid biosynthesis and turnover, as has been described in detail for S. aureus (69). In this organism, every ninth lipid on the outer leaflet of the membrane is an LTA molecule with an average length of 25 GroP units (69). It has been estimated that the PG pool is turned over more than twice per generation time to support LTA synthesis (69). For each PG molecule that is hydrolyzed to extend the LTA chain by one repeating unit, one molecule of DAG is produced. DAG then reenters the cell, where it is recycled to PG or used for the synthesis of glycolipids (Figure 2). In the first step of the recycling process, the cytoplasmic enzyme DgkB converts DAG to phosphatidic acid (57, 58, 90) (Figure 2). Phosphatidic acid is subsequently converted to PG via the conventional PG synthesis pathway by the successive actions of the phosphatidate cytidyltransferase CdsA, the phosphatidylglycerol phosphate synthase PgsA, and one or more enzymes with phosphatidylglycerol phosphate phosphatase activity that convert phosphatidylglycerol phosphate to PG (Figure 2). Although three enzymes, PgpA, PgpB, and PgpC (52, 53, 78), with this activity have been characterized in E. coli, the enzyme(s) with such activity has not yet been identified in gram-positive bacteria. www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 85 MI68CH05-Grundling ARI 26 April 2014 Gal: galactose GlcNAc: N-acetylglucosamine Forssman antigen: An antigen that has the ability to induce rabbits to form hemolytic antibodies to sheep red blood cells Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. D-Ala: D-alanine 15:26 DgkB activity is essential for the growth of B. subtilis; in a conditional dgkB mutant strain, LTA synthesis ceased and DAG accumulated rapidly (57). However, the lethality was prevented by the disruption of either of the two main LTA synthase enzymes, YflE or YfnI (87). Thus, DgkB activity and the DAG recycling pathway are only essential in cells with a high PG turnover caused by LTA synthesis, potentially indicating that the accumulation of DAG is not tolerated by the cell. However, inactivation of YfnI does not result in a decrease in DAG levels, and therefore the accumulation of DAG alone cannot explain the growth arrest seen in the dgkB mutant (87). Complex LTA Structures Several gram-positive bacteria produce more complex LTA polymers, here referred to as type II–V LTAs (Figure 1). Significant progress has been made toward understanding the structure, synthesis, and function of type IV LTA found in Streptococcus pneumoniae (see the following section). As with type IV LTA, the chemical structures of type II, III, and V LTAs may undergo further revisions once they are subjected to additional analysis. It is also likely that additional complex LTAs will be discovered. Type II LTA, found in Lactococcus garvieae strain Kiel 4217, has a proposed backbone of α-Gal(1–6)-α-Gal(1–3)-GroP repeating units in which the GroP units can be further substituted with α-Gal residues (68). The polymer is linked via an α-Glc(1–2)-α-Glc(1–3)-DAG anchor to the membrane, and the first glucose (Glc) molecule can carry an additional acyl chain (68) (Figure 1). Type III LTA, found in Clostridium innocuum, has a proposed structure of αGal(1–3)-GroP–repeating units linked via a β-glucosamine(1–3)-α-Glc(1–3)-DAG lipid anchor to the membrane. The GroP residues are substituted with either N-acetylglucosamine (25%) or glucosamine (50%) residues (35). An LTA polymer with yet another structure, type V LTA, has been observed in Peptostreptococcus anaerobius and C. difficile (107, 114). Type V LTA has a proposed structure of α-D-GlcNAc(1–3)-α-D-GlcNAc repeating units linked through C-6 -C-6 phosphodiester bridges. The second N-acetylglucosamine (GlcNAc) residue is further decorated with D–glyceric acid, and the polymer is retained in the membrane via a β-1-6-linked triglucosylDAG glycolipid anchor (107) (Figure 1). The enzymes involved in type II, III, and V LTA synthesis are unknown. When and if the structures are confirmed, the definition of LTA as alditolphosphatecontaining polymers might need to be revised to include glycosyl-phosphate-containing polymers such as type V LTA. Streptococcus Pneumoniae (Type IV) LTA Type IV LTA is found in S. pneumoniae and some other Streptococcus spp. Pneumococcal LTA (pnLTA) was described in 1930 as pneumococcal C-polysaccharide (119) and was later shown to possess Forssman antigenicity (41). This observation was only explained in 2008, when a revised structure with two terminal GlcNAc residues was proposed; these represent the minimal Forssman antigen (111). In 2013, additional revisions were proposed (40), and it is now assumed that the backbone consists of pseudopentasaccharide repeating units made up of 2-acetamido-4-amino2,4,6-trideoxy-D-galactose (AATGal), Glc, RboP, and two GlcNAc residues (Figure 1). The repeating units are α-1-4-linked to each other and β-1-4-linked to the glycolipid anchor αGlc-(1–3)-DAG (40, 111). It was further suggested that pnLTA contains only D-alanine (D-Ala) modifications on the RboP residues and is not glycosylated, as originally proposed (40, 71). Most bacteria containing LTA also synthesize WTA. On the one hand, in organisms with type I LTA, the two polymers have different structures and are synthesized by different enzymes. pnLTA and pnWTA, on the other hand, have identical structures and are produced by the same enzyme machinery. A detailed model for their synthesis has been proposed (Figure 3) (29); however, many 86 Percy · Gründling Changes may still occur before final publication online and in print MI68CH05-Grundling ARI 26 April 2014 15:26 P Spr 1222 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. Spr P 1655 PP Spr 0091 P P UDP- UMP UDP- UDP AATGal Glc LicD3 P P Spr 1223 P P LicD1 Spr 1224 LicD2 2x 2x CDP- CMP UDP- UDP RboP GalNAc P P P P LCP LCP TacF P P CDP- CMP Cho Figure 3 Type IV LTA synthesis machinery in Streptococcus pneumoniae. The enzymes Spr1655, Spr0091, LicD3 and Spr1123, and Spr1124 use the indicated nucleotide-activated sugars or ribitolphosphate (RboP) as substrate for the synthesis of the C55 -P-linked pseudopentasaccharide intermediate. The N-acetylglucosamine (GlcNAc) residues are decorated with phosphocholine (P-Cho) residues by LicD1 and LicD2. The chain is polymerized by Spr1222, transported across the membrane by TacF, and transferred onto either the glycolipid Glc-DAG (LTA) or peptidoglycan (WTA) by LCP family enzymes. This figure was adapted with permission from Denapaite et al. (29) The publisher for this copyrighted material is Mary Ann Liebert, Inc., publishers. Abbreviations: Glc-DAG, glucosyl-diacylglycerol; LCP, LytR-CpsA-Psr; LTA, lipoteichoic acid. enzymes have not been verified experimentally. The pseudopentasaccharide repeating units are produced on undecaprenyl phosphate (C55 -P), and the GlcNAc residues are further decorated with phosphocholine (P-Cho) residues. The chain is polymerized and then transported across the membrane by TacF, where it is either transferred onto the glycolipid Glc-(1–3)-DAG (LTA) or onto peptidoglycan (WTA), likely by enzymes belonging to the LytR-CpsA-Psr (LCP) family (29, 62). Streptococcus mitis also produces type IV LTA (12). Interestingly, bioinformatics analysis indicated the presence of an LtaS homolog (29), and further investigation is needed to determine whether this species produces both type I and IV LTAs. MODIFICATIONS OF LTAS AND THEIR FUNCTIONS D-Alanylation of LTA Type I and IV LTAs (and WTAs) are modified with D-Ala residues, and the enzymes required for this process are encoded by the dltABCD operon (46, 95). The D-alanylation process starts in the cytoplasm of the cell, where the D-alanine-D-alanyl carrier protein ligase DltA activates D-Ala using ATP to form a high-energy D-alanyl-AMP intermediate and subsequently transfers it to the phosphopantheinyl prostetic group of the D-Ala carrier protein DltC (Figure 4a) (30, 98, 134). DltC shows sequence and structural homology to acyl carrier proteins (ACPs) (124), and structural studies on DltA have shown that this protein belongs to the adenylate-forming www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print C55 -P: undecaprenylphosphate P-Cho: phosphocholine 87 MI68CH05-Grundling ARI 26 April 2014 15:26 enzyme family (30, 98, 134). DltA is assumed to undergo major structural rearrangements during the reaction cycle that are driven by small changes in electrostatic interactions introduced by substrate binding and product formation. The function of the remaining proteins, DltB and DltD, is not completely understood, and different models have been proposed (27, 95, 100). Recent work has provided experimental support for a model originally proposed by Werner Fischer and colleagues (34, 100, 104). In this model, the multiple-membrane-spanning protein DltB transfers a P DltD Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. P DltB P DltC O D-Ala DltA NH3+ NH3+ O H HO ADP H HO ATP b P ? GT-A P GT-C GlcNAc OH OH UDP OH O UDP NHAc c OH N+ P P LicB LicA OH N+ N+ CDP LicC P P LicD1 P P N+ LicD2 Choline ATP ADP 88 Percy · P-Cho CTP PP CDP-Cho CMP Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 the D-Ala from DltC to C55 -P and subsequently transports the D-Ala-P-C55 intermediate across the membrane (Figure 4a). DltB has been grouped among membrane-bound O-acyltransferase (MBOAT) proteins, where other members are known to transfer organic acids onto hydroxyl groups of membrane-embedded components or reacylate lysophospholipids (50, 112). DltD has, as recently shown, an N-in C-out membrane topology placing the functional part of the protein on the outside of the cell (104). In a previous study, thioesterase activity was ascribed to DltD on a cytoplasmic substrate and was unrelated to this pathway (27). The new findings and the location of DltD on the outside of the cell, however, might suggest that this protein is the enzyme that aids in the final step and transfers the D-Ala onto LTA (Figure 4a). A number of environmental factors have been shown to influence the amount of D-alanines on LTA. An increase in pH (79), temperature (51), or NaCl (37) leads to a decrease in D-alanylation. At high pH the ester linkage is labile. The half-life of D-alanines on LTA is 3.9 h at pH 8, whereas it is >10,000 h at pH 6 (20). Two-component systems play a crucial role in regulating the expression of the dlt operon. In S. aureus, the expression of the dlt operon is repressed by ArlSR, in response to an increase in the concentration of Mg2+ (70). The response is, however, species specific: An increase in Mg2+ or K+ has no effect on dlt gene expression in Streptococcus gondii (89). The LiaSR two-component system, which responds to cell membrane damage (115), induces the expression of the dlt operon in response to polymyxin B as well as low pH in S. gondii (89), and in Streptococcus agalactiae, dlt expression is controlled by the DltRS system (103). Analysis of dlt mutants in diverse bacteria revealed that this modification plays an important role in the regulation of autolysis (99, 113), cation homeostasis through the binding of Mg2+ ions (5), host cell adhesion and invasion (1, 72), and biofilm formation (32) and is essential for the virulence of pathogens such as L. monocytogenes and S. aureus (1, 21). In addition, D-alanylation of TAs provides resistance to cationic antimicrobial peptides (CAMPs) (1, 102). It has been presumed that the presence of D-alanines raises the overall net negative charge of the membrane, thereby reducing the affinity for CAMPs. However a recent study on Streptococcus pyogenes questioned the link between charge and the ability of CAMPs to cross the membrane, suggesting instead that the D-alanines alter the conformation of LTA, leading to an increase in the density of the cell wall (109) (see also sidebar, Amino Acid Modifications of Lipopolysaccharides in Gram-Negative Bacteria). Glycosylation of LTA A mechanism for the incorporation of glycosyl residues into type I LTA has been proposed based on work performed in the 1980s (34, 55, 81, 133). Some but not all type I LTAs are glycosylated, and variations are also observed in the type of sugar used for this modification. This has been ←−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Figure 4 LTA modifications. (a) D-Ala modification mechanism of type I and IV LTAs based on the Fischer model (100). DltA ligates D-alanines onto DltC. The D-alanines are transferred onto undecaprenyl phosphate (C55 -P) and subsequently transported across the membrane by DltB. DltD then aids in the transfer of the D-alanines to glycerolphosphate (GroP) of type I or ribitolphosphate (RboP) of type IV LTA. (b) Proposed glycosylation mechanism of type I LTA. A cytoplasmic glycosyltransferase (likely a GT-A member) uses a nucleotide-activated sugar such as UDP-GlcNAc and links it onto C55 -P. The intermediate is transported across the membrane and an extracellular glycosyltransferase (likely a GT-C member) then transfers the sugar onto LTA. (c) Phosphocholine (P-Cho) modification mechanism of type IV LTA. Choline is transported into the cell by LicB and converted to P-Cho and CDP-Cho by the action of LicA and LicC. The enzymes LicD1 and LicD2 then use CDP-Cho to substitute the N-acetylglucosamine (GlcNAc) residues of the TA precursors with P-Cho residues. Abbreviation: LTA, lipoteichoic acid. www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 89 MI68CH05-Grundling ARI 26 April 2014 15:26 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. AMINO ACID MODIFICATIONS OF LIPOPOLYSACCHARIDES IN GRAM-NEGATIVE BACTERIA Proteins with homology to DltA–D have been detected in some gram-negative bacteria belonging to the genera Erwinia, Photorhabdus, and Bordetella (2). The genes were likely acquired by horizontal gene transfer, as their CG content differs from that of the rest of the genome. A Bordetella pertussis strain with a deletion of this D-alanine incorporation and resistance to AMPs, or dra, operon has been produced (2). Reminiscent of phenotypes observed for dlt mutants in gram-positive bacteria, the dra mutant showed increased susceptibility to antimicrobial peptides and was killed more readily by human phagocytes. Initial experiments suggest that outer membrane proteins might be the targets of this modification (2). Another amino acid modification has been observed on the lipid A anchor of lipopolysaccharide in Vibrio cholerae and compared to the Dlt system in gram-positive bacteria (45). Three proteins, AlmE–G, are required for the introduction of these glycine and diglycine modifications. AlmE shows sequence homology to DltA, and it activates and transfers the glycines onto the small carrier protein AlmF (45). AlmF does not show sequence homology to DltC but has been suggested to possess a similar fold. The glycine residues are then transferred from AlmF onto the lipid A anchor by AlmG (45). best characterized for Bacillus strains, where some strains lack glycosyl groups and some contain GlcNAc, whereas others have α-Gal residues on their LTA (54, 55). The LTA of all Listeria strains investigated to date is glycosylated with α-Gal, although the degree of glycosylation can vary between strains (48, 123). There is also some evidence that the LTA of S. aureus strain H is glycosylated with GlcNAc (4); however, other strains lack this modification. Early biochemical studies have shown that the glycosylation process of LTA involves two separate glycosyltransferases and proceeds through the formation of a sugar-linked C55 -P lipid intermediate (Figure 4b) (81, 133). These studies led to the following model: First a cytoplasmic glycosyltransferase uses a nucleotide-activated sugar to form the sugar-P-C55 intermediate. After the transport of this intermediate across the membrane, a second glycosyltransferase links the sugar onto LTA (34, 133) (Figure 4b). The enzymes involved have not yet been identified, however the types of glycosyltransferases required for this process can be speculated upon based on similarities to the modification of lipopolysaccharide (LPS) in Escherichia coli with 4-amino-4deoxy-L-arabinose (L-Ara4N) or the glycosylation of complex cell wall polymers in Mycobacterium tuberculosis (3, 11, 16). The GT-A-type glycosyltransferase ArnC of E. coli uses a UDP-activated sugar to produce a sugar-P-C55 membrane intermediate (16). A GT-A-type glycosyltransferase is therefore a good candidate enzyme that could act as the cytoplasmic glycosyltransferase in the LTA glycosylation process, and proteins homologous to ArnC can be found in a range of gram-positive bacteria. On the outside of the cell, the E. coli ArnT protein, a glycosyltransferase of the GT-C type, transfers the sugar from the C55 -P membrane intermediate onto the lipid A moiety of LPS. GT-C fold glycosyltransferases have not been characterized in much detail; proteins belonging to this family usually contain 8–13 transmembrane helices but share only limited homology (73, 76). However, GT-C enzymes use C55 -P-linked sugars as a substrate, and therefore we suggest that the extracellular glycosyltransferase involved in LTA glycosylation likely belongs to this enzyme family. Phosphocholine Modification of Type IV LTA LPS: lipopolysaccharide Type IV LTA in S. pneumoniae is modified with P-Cho residues (29, 120). In contrast to Dalanylation, this modification is essential for bacterial growth. The P-Cho residues are introduced 90 Percy · Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 into the TA precursors within the cytoplasm of the cell, and it is assumed that the polymer is only exported once it is modified with P-Cho (26). Choline is transported into the cell by LicB and converted into P-Cho and subsequently CDP-Cho by LicA and LicC, respectively, and then attached to the O-6 position of one or both GalNAc residues by the enzymes LicD1 and LicD2 (Figure 4c) (10, 31, 36, 135). Once the modified polymer is exported, the P-Cho content can be reduced by the phosphorylcholine esterase Pce (47, 125). Because of the structure of its active site, this enzyme is only capable of removing the terminal choline residues, and it has been suggested that the reduction in choline residues exposed on the bacterial surface is important to prevent the interaction with host immune proteins (47). The growth requirement of S. pneumoniae for choline can be counteracted by the addition of other amino-alcohols such as ethanolamine, although cells grown under these conditions have various morphological defects and are attenuated in virulence (121). The amino-alcohol physically replaces the P-Cho residues on the TAs, but it cannot replace them functionally. Several cell wall proteins, collectively referred to as choline-binding proteins (CBPs), require P-Cho for their retention in the cell wall or even activity, as in the case of LytA (38, 122). CBPs are modular enzymes that in several cases contain a peptidoglycan hydrolase domain and a variable number of cholinebinding domains (38). These enzymes are required for the remodeling of the peptidoglycan, autolysis, and natural competence (122). Structural analyses of CBPs have provided insight into the binding and substrate specificity of this class of enzymes (47, 92, 101). CBPs also play a significant role in the virulence of S. pneumoniae, as some CBPs, including PspA, PspC, and CbpG, mediate interactions with host cells (64, 82, 96, 126). PspA has an additional function: It also prevents complement deposition on the pneumococcal surface by inhibiting the binding of the C-reactive host immune protein (CRP) to bacteria by competing for P-Cho-binding sites (93). Taken together, these findings make it clear that the P-Cho modifications on TAs play a key role in bacterial physiology and the virulence of S. pneumoniae; however, it should be noted that one cannot distinguish between the requirement of this modification on LTA versus WTA. APPLICATIONS OF LTA AND MUTANT STRAINS Several lines of research that are currently being pursued could be of direct clinical relevance. LTA polymers and specific antibodies against these polymers have been tested as vaccine candidates. Immunization of mice with gram-positive bacteria or purified LTA has been shown to elicit the production of opsonic antibodies (67, 117). To increase the immunogenicity of LTAs, the production of conjugate vaccines is currently being pursued. Recent studies have reported on the synthesis of a conjugate between synthetic type I LTA and the immunogenic tetanus toxin protein or between type V LTA of C. difficile with E. coli enterotoxin or a Pseudomonas exotoxin (13, 18, 25). Much effort has gone into the use of type I LTA–specific antibodies in passive immunization studies (118, 129, 130). A humanized antibody has been used in human trials in very-low-weight neonates, and the vaccine appeared safe and well tolerated; however, no clear protection was observed against staphylococcal sepsis in this study (129, 130). Enzymes involved in LTA synthesis and their modifications can also be exploited as antimicrobial targets. For instance, choline analogues have been shown to bind to and inhibit the activity of pneumococcal CBPs (80, 83). A d-Ala analog that blocks the activity of DltA in vitro has been shown to synergize with the peptidoglycan synthesis inhibitor vancomycin and lead to growth inhibition when used in combination (88). Recently, an LtaS enzyme inhibitor was identified (108). This small molecule was shown to prevent the growth of S. aureus and several other antibiotic-resistant gram-positive bacteria (108). Mice challenged with a lethal dose of S. aureus showed increased survival in the presence of this compound (108). The identification of the genetic determinants required for www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 91 MI68CH05-Grundling ARI 26 April 2014 15:26 LTA production made it possible to compare the interaction of wild-type and LTA-deficient bacteria with immune cells. Recent work using an LTA-negative L. acidophilus strain highlighted the potential use of such a mutant as a probiotic strain with improved properties (75). In contrast to wild-type L. acidophilus, the ltaS mutant strain was shown to downregulate the production of the inflammatory cytokines IL-12 and TNFα and enhance the production of the anti-inflammatory cytokine IL-10 (91). Colonization of mice with the LTA-deficient L. acidophilus strain also showed promising results: This treatment mitigated the effects of induced colitis, highlighting the potential use of such a strain for the treatment of inflammatory intestinal disorders (91). More recently, its application in preventing colon cancer is also being pursued (65). COMPARISON OF TYPE I LTA AND OSMOREGULATED PERIPLASMIC GLUCAN SYNTHESIS Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. LTA is often compared to LPS of gram-negative bacteria. In particular for type I LTA, it might be more appropriate to compare this polymer to OPGs of gram-negative bacteria, based on similarities between enzymes involved in their synthesis, their cellular location within the periplasm [they are not surface-exposed molecules (105)], and their function in osmoprotection. OPGs, formerly referred to as membrane-derived oligosaccharides (MDOs), are oligosaccharides that accumulate under low osmolarity conditions in the periplasm of gram-negative bacteria (63). In E. coli, linear β(1–2)-linked glucose units are produced as lipid-linked intermediates by the glycosyltransferase OpgH. Similar to the LTA glycolipid anchor–producing enzyme YpfP of S. aureus (or UgtP of B. subtilis), this enzyme uses UDP-glucose as a substrate. OpgH has also been shown to play a key role in nutrient-dependent and UDP-glucose-concentration-dependent cell size control in E. coli (49). A similar function has been previously reported for the B. subtilis UgtP enzyme through regulating the polymerization of the cell division protein FtsZ (19, 127). The linear lipid-linked glucose chains are then transported to the outer leaflet of the inner membrane where the periplasmically located glycosyltransferase OpgG adds β(1–6)-linked glucose branches. The oligosaccharides are then decorated with succinyl, phosphoethanolamine, and GroP residues by the action of OpgC, OpgE, and OpgB, respectively (15, 63). OpgB, also referred to as MdoB, shares many features with LtaS-type enzymes. Both enzymes consist of an N-terminal transmembrane and a C-terminal extracellular enzymatic domain (74). Similar to LtaS, OpgB is processed during bacterial growth by a protease speculated to be the signal peptidase, and the enzymatic domain is released into the periplasmic space (74). Both enzymes are Mn2+ -dependent metal enzymes that use the lipid PG as substrate to add the GroP units onto the periplasmic oligosaccharides or onto the glycolipid anchor, respectively (42, 56). In both instances, this leads to a rapid PG lipid turnover and the requirement of a functional lipid-recycling pathway. Based on cryoelectron microscopy images, LTA has been suggested to be an important constituent of the inner cell wall zone also referred to as the gram-positive periplasm (84–86). OPGs accumulate in the gram-negative periplasm in low-osmolarity medium and are thought to protect bacteria under these conditions, although only modest growth defects have been observed in their absence (14, 63). The observation that an S. aureus strain lacking LTA can be rescued in high-osmolality medium or by an increase in the cellular c-di-AMP concentration, implicated in the control of ion transport (22, 23, 97), might indicate a similar function for LTA in the osmoprotection of the cell. CONCLUSIONS LTA represents a significant proportion of the cell membrane and inner cell wall zone in grampositive bacteria. It plays an important role in bacterial growth and physiology and contributes to 92 Percy · Gründling Changes may still occur before final publication online and in print MI68CH05-Grundling ARI 26 April 2014 15:26 membrane homeostasis and virulence. Although we now have a good understanding of type I and IV LTA synthesis and their modifications with D-Ala and P-Cho residues, more work is needed on the glycosylation mechanism and the synthesis pathways of other complex LTAs. Recent advances in the field have allowed the investigation of these polymers as vaccine candidates, LTA mutant strains as probiotics with improved characteristics, and LTA synthesis enzymes as novel antimicrobial targets. SUMMARY POINTS Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. 1. LTA is defined as an alditolphosphate-containing polymer that is linked via a lipid anchor to the outside of the membrane in gram-positive bacteria. However, this definition may need to be revised to include recently described complex glycosyl-phosphate containing polymers. 2. LTAs have been grouped into different types based on their chemical structures. Type I LTA has a simple unbranched polyglycerolphosphate backbone structure whereas type II–V LTAs have more complex structures. 3. Type I polyglycerolphosphate LTA production is intimately linked with membrane lipid turnover, and its synthesis shows striking similarities to the production of osmoregulated periplasmic glucans in gram-negative bacteria. 4. LTA plays an important role for bacterial growth and physiology and contributes to membrane homeostasis and virulence. 5. The essential nature of LTA makes it an attractive target for vaccines and novel antimicrobials. FUTURE ISSUES 1. Based on bioinformatics analysis, several enzymes have been predicted to be involved in type IV LTA synthesis; however, these need to be confirmed experimentally. 2. Further analysis is needed to confirm the chemical structures of other complex LTA types, and the enzymes required for their synthesis need to be identified. 3. DltB is thought to produce a D-Ala-P-C55 membrane intermediate, and DltD is thought to transfer D-Ala onto LTA; however, these activities need to be confirmed experimentally. 4. The genetic determinants required for the glycosylation process of LTA need to be identified and a function for this modification elucidated. 5. Further work is needed to validate LTA synthesis enzymes as a therapeutic target, LTA polymers as vaccine candidates, and LTA mutant strains as probiotics with improved characteristics. DISCLOSURE STATEMENT The authors are not aware of any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this review. www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 93 MI68CH05-Grundling ARI 26 April 2014 15:26 ACKNOWLEDGMENTS Work in the A.G. laboratory is currently supported by the European Research Council grant 260371 and the Wellcome Trust grant 100289. LITERATURE CITED Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. 1. Abachin E, Poyart C, Pellegrini E, Milohanic E, Fiedler F, et al. 2002. Formation of D-alanyl-lipoteichoic acid is required for adhesion and virulence of Listeria monocytogenes. Mol. Microbiol. 43:1–14 2. Abi Khattar Z, Rejasse A, Destoumieux-Garzón D, Escoubas JM, Sanchis V, et al. 2009. The dlt operon of Bacillus cereus is required for resistance to cationic antimicrobial peptides and for virulence in insects. J. Bact. 191:7063–73 3. Alderwick LJ, Lloyd GS, Ghadbane H, May JW, Bhatt A, et al. 2011. The C-terminal domain of the arabinosyltransferase Mycobacterium tuberculosis EmbC is a lectin-like carbohydrate binding module. PLoS Pathog. 7:e1001299 4. Arakawa H, Shimada A, Ishimoto N, Ito E. 1981. Occurrence of ribitol-containing lipoteichoic acid in Staphylococcus aureus H and its glycosylation. J. Biochem. 89:1555–63 5. Archibald AR, Baddiley J, Heptinstall S. 1973. The alanine ester content and magnesium binding capacity of walls of Staphylococcus aureus H grown at different pH values. Biochim. Biophys. Acta 291:629–34 6. Armstrong JJ, Baddiley J, Buchanan JG, Davision AL, Kelemen MV, Neuhaus FC. 1958. Isolation and structure of ribitol phosphate derivatives (teichoic acids) from bacterial cell walls. J. Chem. Soc. 1958:4344–54 7. Armstrong JJ, Baddiley J, Buchanan JG, Davision AL, Kelemen MV, Neuhaus FC. 1959. Composition of teichoic acids from a number of bacterial walls. Nature 184:247–48 8. Baddiley J. 1972. Teichoic acids in cell walls and membranes of bacteria. Essays Biochem. 8:35–77 9. Bai Y, Yang J, Zarrella TM, Zhang Y, Metzger DW, Bai G. 2013. Cyclic di-AMP impairs potassium uptake mediated by a cyclic di-AMP binding protein in Streptococcus pneumoniae. J. Bact. 196:614–23 10. Baur S, Marles-Wright J, Buckenmaier S, Lewis RJ, Vollmer W. 2009. Synthesis of CDP-activated ribitol for teichoic acid precursors in Streptococcus pneumoniae. J. Bact. 191:1200–10 11. Berg S, Kaur D, Jackson M, Brennan PJ. 2007. The glycosyltransferases of Mycobacterium tuberculosis— roles in the synthesis of arabinogalactan, lipoarabinomannan, and other glycoconjugates. Glycobiology 17:35R–56R 12. Bergström N, Jansson PE, Kilian M, Skov Sørensen UB. 2000. Structures of two cell wall-associated polysaccharides of a Streptococcus mitis biovar 1 strain: a unique teichoic acid-like polysaccharide and the group O antigen which is a C-polysaccharide in common with pneumococci. Eur. J. Biochem. 267:7147– 57 13. Bertolo L, Boncheff AG, Ma Z, Chen YH, Wakeford T, et al. 2012. Clostridium difficile carbohydrates: glucan in spores, PSII common antigen in cells, immunogenicity of PSII in swine and synthesis of a dual C. difficile–ETEC conjugate vaccine. Carbohydr. Res. 354:79–86 14. Bhagwat AA, Jun W, Liu L, Kannan P, Dharne M, et al. 2009. Osmoregulated periplasmic glucans of Salmonella enterica serovar Typhimurium are required for optimal virulence in mice. Microbiology 155:229–37 15. Bontemps-Gallo S, Cogez V, Robbe-Masselot C, Quintard K, Dondeyne J, et al. 2013. Biosynthesis of osmoregulated periplasmic glucans in Escherichia coli: The phosphoethanolamine transferase is encoded by opgE. BioMed. Res. Int. 2013:371429 16. Breazeale SD, Ribeiro AA, McClerren AL, Raetz CR. 2005. A formyltransferase required for polymyxin resistance in Escherichia coli and the modification of lipid A with 4-amino-4-deoxy-L-arabinose: identification and function of UDP-4-deoxy-4-formamido-L-arabinose. J. Biol. Chem. 280:14154–67 17. Brown S, Santa Maria JP Jr, Walker S. 2013. Wall teichoic acids of gram-positive bacteria. Annu. Rev. Microbiol. 67:313–36 18. Chen Q, Dintaman J, Lees A, Sen G, Schwartz D, et al. 2013. Novel synthetic (poly)glycerolphosphatebased antistaphylococcal conjugate vaccine. Infect. Immun. 81:2554–61 94 Percy · Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 19. Chien AC, Zareh SK, Wang YM, Levin PA. 2012. Changes in the oligomerization potential of the division inhibitor UgtP co-ordinate Bacillus subtilis cell size with nutrient availability. Mol. Microbiol. 86:594–610 20. Childs WC III, Neuhaus FC. 1980. Biosynthesis of D-alanyl-lipoteichoic acid: characterization of esterlinked D-alanine in the in vitro-synthesized product. J. Bact. 143:293–301 21. Collins LV, Kristian SA, Weidenmaier C, Faigle M, Van Kessel KP, et al. 2002. Staphylococcus aureus strains lacking D-alanine modifications of teichoic acids are highly susceptible to human neutrophil killing and are virulence attenuated in mice. J. Infect. Dis. 186:214–19 22. Corrigan RM, Abbott JC, Burhenne H, Kaever V, Gründling A. 2011. c-di-AMP is a new second messenger in Staphylococcus aureus with a role in controlling cell size and envelope stress. PLoS Pathog. 7:e1002217 23. Corrigan RM, Campeotto I, Jeganathan T, Roelofs KG, Lee VT, Gründling A. 2013. Systematic identification of conserved bacterial c-di-AMP receptor proteins. Proc. Natl. Acad. Sci. USA 110:9084–89 24. Corrigan RM, Gründling A. 2013. Cyclic di-AMP: another second messenger enters the fray. Nat. Rev. Microbiol. 11:513–24 25. Cox AD, St. Michael F, Aubry A, Cairns CM, Strong PC, et al. 2013. Investigating the candidacy of a lipoteichoic acid-based glycoconjugate as a vaccine to combat Clostridium difficile infection. Glycoconj. J. 30:843–55 26. Damjanovic M, Kharat AS, Eberhardt A, Tomasz A, Vollmer W. 2007. The essential tacF gene is responsible for the choline-dependent growth phenotype of Streptococcus pneumoniae. J. Bact. 189:7105– 11 27. Debabov DV, Kiriukhin MY, Neuhaus FC. 2000. Biosynthesis of lipoteichoic acid in Lactobacillus rhamnosus: role of DltD in D-alanylation. J. Bact. 182:2855–64 28. Dehus O, Pfitzenmaier M, Stuebs G, Fischer N, Schwaeble W, et al. 2011. Growth temperaturedependent expression of structural variants of Listeria monocytogenes lipoteichoic acid. Immunobiology 216:24–31 29. Denapaite D, Brückner R, Hakenbeck R, Vollmer W. 2012. Biosynthesis of teichoic acids in Streptococcus pneumoniae and closely related species: lessons from genomes. Microb. Drug Resist. 18:344–58 30. Du L, He Y, Luo Y. 2008. Crystal structure and enantiomer selection by D-alanyl carrier protein ligase DltA from Bacillus cereus. Biochemistry 47:11473–80 31. Eberhardt A, Wu LJ, Errington J, Vollmer W, Veening JW. 2009. Cellular localization of cholineutilization proteins in Streptococcus pneumoniae using novel fluorescent reporter systems. Mol. Microbiol. 74:395–408 32. Fabretti F, Theilacker C, Baldassarri L, Kaczynski Z, Kropec A, et al. 2006. Alanine esters of enterococcal lipoteichoic acid play a role in biofilm formation and resistance to antimicrobial peptides. Infect. Immun. 74:4164–71 33. Fischer W. 1990. Bacterial phosphoglycolipids and lipoteichoic acids. In Handbook of lipid research, ed. D Hanahan, pp. 123–234. New York: Plenum 34. Fischer W. 1994. Lipoteichoic acid and lipids in the membrane of Staphylococcus aureus. Med. Microbiol. Immunol. 183:61–76 35. Fischer W. 1994. Lipoteichoic acids and lipoglycans. In Bacterial Cell Wall, ed. JM Ghuysen, R Hackenbeck, pp. 199–214. Amsterdam: Elsevier Science 36. Fischer W. 2000. Phosphocholine of pneumococcal teichoic acids: role in bacterial physiology and pneumococcal infection. Res. Microbiol. 151:421–27 37. Fischer W, Rösel P. 1980. The alanine ester substitution of lipoteichoic acid (LTA) in Staphylococcus aureus. FEBS Lett. 119:224–26 38. Gárcia JL, Sánchez-Beato AR, Medrano FJ, López R. 1998. Versatility of choline-binding domain. Microb. Drug Resist. 4:25–36 39. Garufi G, Hendrickx AP, Beeri K, Kern JW, Sharma A, et al. 2012. Synthesis of lipoteichoic acids in Bacillus anthracis. J. Bact. 194:4312–21 40. Gisch N, Kohler T, Ulmer AJ, Müthing J, Pribyl T, et al. 2013. Structural reevaluation of Streptococcus pneumoniae lipoteichoic acid and new insights into its immunostimulatory potency. J. Biol. Chem. 288:15654–67 www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 95 ARI 26 April 2014 15:26 41. Goebel WF, Adams MH. 1943. The immunological properties of the heterophile antigen and somatic polysaccharide of pneumococcus. J. Exp. Med. 77:435–49 42. Goldberg DE, Rumley MK, Kennedy EP. 1981. Biosynthesis of membrane-derived oligosaccharides: a periplasmic phosphoglyceroltransferase. Proc. Natl. Acad. Sci. USA 78:5513–17 43. Gründling A, Schneewind O. 2007. Genes required for glycolipid synthesis and lipoteichoic acid anchoring in Staphylococcus aureus. J. Bacteriol. 189:2521–30 44. Gründling A, Schneewind O. 2007. Synthesis of glycerol phosphate lipoteichoic acid in Staphylococcus aureus. Proc. Natl. Acad. Sci. USA 104:8478–83 45. Hankins JV, Madsen JA, Giles DK, Brodbelt JS, Trent MS. 2012. Amino acid addition to Vibrio cholerae LPS establishes a link between surface remodeling in gram-positive and gram-negative bacteria. Proc. Natl. Acad. Sci. USA 109:8722–27 46. Heaton MP, Neuhaus FC. 1992. Biosynthesis of D-alanyl-lipoteichoic acid: cloning, nucleotide sequence, and expression of the Lactobacillus casei gene for the D-alanine-activating enzyme. J. Bacteriol. 174:4707–17 47. Hermoso JA, Lagartera L, González A, Stelter M, Garcı́a P, et al. 2005. Insights into pneumococcal pathogenesis from the crystal structure of the modular teichoic acid phosphorylcholine esterase Pce. Nat. Struct. Mol. Biol. 12:533–38 48. Hether NW, Jackson LL. 1983. Lipoteichoic acid from Listeria monocytogenes. J. Bact. 156:809–17 49. Hill NS, Buske PJ, Shi Y, Levin PA. 2013. A moonlighting enzyme links Escherichia coli cell size with central metabolism. PLoS Genet. 9:e1003663 50. Hofmann K. 2000. A superfamily of membrane-bound O-acyltransferases with implications for Wnt signaling. Trends Biochem. Sci. 25:111–12 51. Hurst A, Hughes A, Duckworth M, Baddiley J. 1975. Loss of D-alanine during sublethal heating of Staphylococcus aureus S6 and magnesium binding during repair. J. Gen. Microbiol. 89:277–84 52. Icho T. 1988. Membrane-bound phosphatases in Escherichia coli: sequence of the pgpB gene and dual subcellular localization of the pgpB product. J. Bacteriol. 170:5117–24 53. Icho T, Raetz CR. 1983. Multiple genes for membrane-bound phosphatases in Escherichia coli and their action on phospholipid precursors. J. Bacteriol. 153:722–30 54. Iwasaki H, Shimada A, Ito E. 1986. Comparative studies of lipoteichoic acids from several Bacillus strains. J. Bacteriol. 167:508–16 55. Iwasaki H, Shimada A, Yokoyama K, Ito E. 1989. Structure and glycosylation of lipoteichoic acids in Bacillus strains. J. Bacteriol. 171:424–29 56. Jackson BJ, Bohin JP, Kennedy EP. 1984. Biosynthesis of membrane-derived oligosaccharides: characterization of mdoB mutants defective in phosphoglycerol transferase I activity. J. Bacteriol. 160:976–81 57. Jerga A, Lu YJ, Schujman GE, de Mendoza D, Rock CO. 2007. Identification of a soluble diacylglycerol kinase required for lipoteichoic acid production in Bacillus subtilis. J. Biol. Chem. 282:21738–45 58. Jerga A, Miller DJ, White SW, Rock CO. 2009. Molecular determinants for interfacial binding and conformational change in a soluble diacylglycerol kinase. J. Biol. Chem. 284:7246–54 59. Jorasch P, Warnecke DC, Lindner B, Zähringer U, Heinz E. 2000. Novel processive and nonprocessive glycosyltransferases from Staphylococcus aureus and Arabidopsis thaliana synthesize glycoglycerolipids, glycophospholipids, glycosphingolipids and glycosylsterols. Eur. J. Biochem. 267:3770–83 60. Jorasch P, Wolter FP, Zähringer U, Heinz E. 1998. A UDP glucosyltransferase from Bacillus subtilis successively transfers up to four glucose residues to 1,2-diacylglycerol: expression of ypfP in Escherichia coli and structural analysis of its reaction products. Mol. Microbiol. 29:419–30 61. Karatsa-Dodgson M, Wörmann ME, Gründling A. 2010. In vitro analysis of the Staphylococcus aureus lipoteichoic acid synthase enzyme using fluorescently labeled lipids. J. Bacteriol. 192:5341–49 62. Kawai Y, Marles-Wright J, Cleverley RM, Emmins R, Ishikawa S, et al. 2011. A widespread family of bacterial cell wall assembly proteins. EMBO J. 30:4931–41 63. Kennedy EP. 1996. Membrane-derived oligosaccharides (periplasmic β-D-glucans) of Escherichia coli. In Escherichia coli and Salmonella, ed. FC Neidhardt, pp. 1064–71. Washington, DC: ASM 64. Kharat AS, Tomasz A. 2006. Drastic reduction in the virulence of Streptococcus pneumoniae expressing type 2 capsular polysaccharide but lacking choline residues in the cell wall. Mol. Biol. 60:93–107 65. Khazaie K, Zadeh M, Khan MW, Bere P, Gounari F, et al. 2012. Abating colon cancer polyposis by Lactobacillus acidophilus deficient in lipoteichoic acid. Proc. Natl. Acad. Sci. USA 109:10462–67 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling 96 Percy · Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 66. Kiriukhin MY, Debabov DV, Shinabarger DL, Neuhaus FC. 2001. Biosynthesis of the glycolipid anchor in lipoteichoic acid of Staphylococcus aureus RN4220: role of YpfP, the diglucosyldiacylglycerol synthase. J. Bacteriol. 183:3506–14 67. Knox KW, Wicken AJ. 1973. Immunological properties of teichoic acids. Bacteriol. Rev. 37:215–57 68. Koch HU, Fischer W. 1978. Acyldiglucosyldiacylglycerol-containing lipoteichoic acid with a poly(3-Ogalabiosyl-2-O-galactosyl-sn-glycero-1-phosphate) chain from Streptococcus lactis Kiel 42172. Biochemistry 17:5275–81 69. Koch HU, Haas R, Fischer W. 1984. The role of lipoteichoic acid biosynthesis in membrane lipid metabolism of growing Staphylococcus aureus. Eur. J. Biochem. 138:357–63 70. Koprivnjak T, Mlakar V, Swanson L, Fournier B, Peschel A, Weiss JP. 2006. Cation-induced transcriptional regulation of the dlt operon of Staphylococcus aureus. J. Bacteriol. 188:3622–30 71. Kovács M, Halfmann A, Fedtke I, Heintz M, Peschel A, et al. 2006. A functional dlt operon, encoding proteins required for incorporation of D-alanine in teichoic acids in gram-positive bacteria, confers resistance to cationic antimicrobial peptides in Streptococcus pneumoniae. J. Bacteriol. 188:5797–805 72. Kristian SA, Datta V, Weidenmaier C, Kansal R, Fedtke I, et al. 2005. D-Alanylation of teichoic acids promotes group A Streptococcus antimicrobial peptide resistance, neutrophil survival, and epithelial cell invasion. J. Bacteriol. 187:6719–25 73. Lairson LL, Henrissat B, Davies GJ, Withers SG. 2008. Glycosyltransferases: structures, functions, and mechanisms. Annu. Rev. Biochem. 77:521–55 74. Lequette Y, Lanfroy E, Cogez V, Bohin JP, Lacroix JM. 2008. Biosynthesis of osmoregulated periplasmic glucans in Escherichia coli: The membrane-bound and the soluble periplasmic phosphoglycerol transferases are encoded by the same gene. Microbiology 154:476–83 75. Lightfoot YL, Mohamadzadeh M. 2013. Tailoring gut immune responses with lipoteichoic acid-deficient Lactobacillus acidophilus. Front. Immunol. 4:25 76. Liu J, Mushegian A. 2003. Three monophyletic superfamilies account for the majority of the known glycosyltransferases. Protein Sci. 12:1418–31 77. Lu D, Wörmann ME, Zhang X, Schneewind O, Gründling A, Freemont PS. 2009. Structure-based mechanism of lipoteichoic acid synthesis by Staphylococcus aureus LtaS. Proc. Natl. Acad. Sci. USA 106:1584–89 78. Lu YH, Guan Z, Zhao J, Raetz CR. 2011. Three phosphatidylglycerol-phosphate phosphatases in the inner membrane of Escherichia coli. J. Biol. Chem. 286:5506–18 79. MacArthur AE, Archibald AR. 1984. Effect of culture pH on the D-alanine ester content of lipoteichoic acid in Staphylococcus aureus. J. Bacteriol. 160:792–93 80. Maestro B, González A, Garcı́a P, Sanz JM. 2007. Inhibition of pneumococcal choline-binding proteins and cell growth by esters of bicyclic amines. FEBS J. 274:364–76 81. Mancuso DJ, Chiu TH. 1982. Biosynthesis of glucosyl monophosphoryl undecaprenol and its role in lipoteichoic acid biosynthesis. J. Bacteriol. 152:616–25 82. Mann B, Orihuela C, Antikainen J, Gao G, Sublett J, et al. 2006. Multifunctional role of choline binding protein G in pneumococcal pathogenesis. Infect. Immun. 74:821–29 83. Martı́n NS, Retamosa MG, Maestro B, Bartual SG, Rodes MJ, et al. 2013. Crystal structures of CbpF complexed with atropine and ipratropium reveal clues for the design of novel antimicrobials against Streptococcus pneumoniae. Biochim. Biophys. Acta 1840:129–35 84. Matias VR, Beveridge TJ. 2005. Cryo-electron microscopy reveals native polymeric cell wall structure in Bacillus subtilis 168 and the existence of a periplasmic space. Mol. Microbiol. 56:240–51 85. Matias VR, Beveridge TJ. 2006. Native cell wall organization shown by cryo-electron microscopy confirms the existence of a periplasmic space in Staphylococcus aureus. J. Bacteriol. 188:1011–21 86. Matias VR, Beveridge TJ. 2008. Lipoteichoic acid is a major component of the Bacillus subtilis periplasm. J. Bacteriol. 190:7414–18 87. Matsuoka S, Hashimoto M, Kamiya Y, Miyazawa T, Ishikawa K, et al. 2011. The Bacillus subtilis essential gene dgkB is dispensable in mutants with defective lipoteichoic acid synthesis. Genes Genet. Syst. 86:365–76 88. May JJ, Finking R, Wiegeshoff F, Weber TT, Bandur N, et al. 2005. Inhibition of the D-alanine: DAlanyl carrier protein ligase from Bacillus subtilis increases the bacterium’s susceptibility to antibiotics that target the cell wall. FEBS J. 272:2993–3003 www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 97 ARI 26 April 2014 15:26 89. McCormick NE, Halperin SA, Lee SF. 2011. Regulation of D-alanylation of lipoteichoic acid in Streptococcus gordonii. Microbiology 157:2248–56 90. Miller DJ, Jerga A, Rock CO, White SW. 2008. Analysis of the Staphylococcus aureus DgkB structure reveals a common catalytic mechanism for the soluble diacylglycerol kinases. Structure 16:1036–46 91. Mohamadzadeh M, Pfeiler EA, Brown JB, Zadeh M, Gramarossa M, et al. 2011. Regulation of induced colonic inflammation by Lactobacillus acidophilus deficient in lipoteichoic acid. Proc. Natl. Acad. Sci. USA 108(Suppl. 1):4623–30 92. Molina R, González A, Stelter M, Pérez-Dorado I, Kahn R, et al. 2009. Crystal structure of CbpF, a bifunctional choline-binding protein and autolysis regulator from Streptococcus pneumoniae. EMBO Rep. 10:246–51 93. Mukerji R, Mirza S, Roche AM, Widener RW, Croney CM, et al. 2012. Pneumococcal surface protein A inhibits complement deposition on the pneumococcal surface by competing with the binding of Creactive protein to cell-surface phosphocholine. J. Immunobiol. 189:5327–35 94. Nelson JW, Sudarsan N, Furukawa K, Weinberg Z, Wang JX, Breaker RR. 2013. Riboswitches in eubacteria sense the second messenger c-di-AMP. Nat. Chem. Biol. 9:834–39 95. Neuhaus FC, Baddiley J. 2003. A continuum of anionic charge: structures and functions of D-alanylteichoic acids in gram-positive bacteria. Microbiol. Mol. Biol. Rev. 67:686–723 96. Ogunniyi AD, LeMessurier KS, Graham RM, Watt JM, Briles DE, et al. 2007. Contributions of pneumolysin, pneumococcal surface protein A (PspA), and PspC to pathogenicity of Streptococcus pneumoniae D39 in a mouse model. Infect. Immunol. 75:1843–51 97. Oku Y, Kurokawa K, Matsuo M, Yamada S, Lee BL, Sekimizu K. 2009. Pleiotropic roles of polyglycerolphosphate synthase of lipoteichoic acid in growth of Staphylococcus aureus cells. J. Bacteriol. 191:141–51 98. Osman KT, Du L, He Y, Luo Y. 2009. Crystal structure of Bacillus cereus D-alanyl carrier protein ligase (DltA) in complex with ATP. J. Mol. Biol. 388:345–55 99. Perea Vélez M, Verhoeven TL, Draing C, Von Aulock S, Pfitzenmaier M, et al. 2007. Functional analysis of D-alanylation of lipoteichoic acid in the probiotic strain Lactobacillus rhamnosus GG. Appl. Environ. Microbiol. 73:3595–604 100. Perego M, Glaser P, Minutello A, Strauch MA, Leopold K, Fischer W. 1995. Incorporation of D-alanine into lipoteichoic acid and wall teichoic acid in Bacillus subtilis. Identification of genes and regulation. J. Biol. Chem. 270:15598–606 101. Pérez-Dorado I, González A, Morales M, Sanles R, Striker W, et al. 2010. Insights into pneumococcal fratricide from the crystal structures of the modular killing factor LytC. Nat. Struct. Mol. Biol. 17:576–81 102. Peschel A, Otto M, Jack RW, Kalbacher H, Jung G, Gotz F. 1999. Inactivation of the dlt operon in Staphylococcus aureus confers sensitivity to defensins, protegrins, and other antimicrobial peptides. J. Biol. Chem. 274:8405–10 103. Poyart C, Lamy MC, Boumaila C, Fiedler F, Trieu-Cuot P. 2001. Regulation of D-alanyl-lipoteichoic acid biosynthesis in Streptococcus agalactiae involves a novel two-component regulatory system. J. Bacteriol. 183:6324–34 104. Reichmann NT, Cassona CP, Gründling A. 2013. Revised mechanism of D-alanine incorporation into cell wall polymers in gram-positive bacteria. Microbiology 159:1868–77 105. Reichmann NT, Cassona CP, Monteiro JM, Bottomley AL, Corrigan RM, et al. 2014. Differential localization of LTA synthesis proteins and their interaction with the cell division machinery in Staphylococcus aureus. Mol. Microbiol. In press. doi: 10.1111/mmi.122551 106. Reichmann NT, Gründling A. 2011. Location, synthesis and function of glycolipids and polyglycerolphosphate lipoteichoic acid in gram-positive bacteria of the phylum Firmicutes. FEMS Microbiol. Lett. 319:97–105 107. Reid CW, Vinogradov E, Li J, Jarrell HC, Logan SM, Brisson JR. 2012. Structural characterization of surface glycans from Clostridium difficile. Carbohydr. Res. 354:65–73 108. Richter SG, Elli D, Kim HK, Hendrickx AP, Sorg JA, et al. 2013. Small molecule inhibitor of lipoteichoic acid synthesis is an antibiotic for gram-positive bacteria. Proc. Natl. Acad. Sci. USA 110:3531–36 109. Saar-Dover R, Bitler A, Nezer R, Shmuel-Galia L, Firon A, et al. 2012. D-Alanylation of lipoteichoic acids confers resistance to cationic peptides in group B Streptococcus by increasing the cell wall density. PLoS Pathog. 8:e1002891 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling 98 Percy · Gründling Changes may still occur before final publication online and in print Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. MI68CH05-Grundling ARI 26 April 2014 15:26 110. Schirner K, Marles-Wright J, Lewis RJ, Errington J. 2009. Distinct and essential morphogenic functions for wall- and lipo-teichoic acids in Bacillus subtilis. EMBO J. 28:830–42 111. Seo HS, Cartee RT, Pritchard DG, Nahm MH. 2008. A new model of pneumococcal lipoteichoic acid structure resolves biochemical, biosynthetic, and serologic inconsistencies of the current model. J. Bacteriol. 190:2379–87 112. Shindou H, Hishikawa D, Harayama T, Yuki K, Shimizu T. 2009. Recent progress on acyl CoA: lysophospholipid acyltransferase research. J. Lipid Res. 50(Suppl.):S46–51 113. Steen A, Palumbo E, Deghorain M, Cocconcelli PS, Delcour J, et al. 2005. Autolysis of Lactococcus lactis is increased upon D-alanine depletion of peptidoglycan and lipoteichoic acids. J. Bacteriol. 187:114–24 114. Stortz CA, Cherniak R, Jones RG, Treber TD, Reinhardt DJ. 1990. Polysaccharides from Peptostreptococcus anaerobius and structure of the species-specific antigen. Carbohydr. Res. 207:101–20 115. Suntharalingam P, Senadheera MD, Mair RW, Lévesque CM, Cvitkovitch DG. 2009. The LiaFSR system regulates the cell envelope stress response in Streptococcus mutans. J. Bacteriol. 191:2973–84 116. Taron DJ, Childs WC III, Neuhaus FC. 1983. Biosynthesis of D-alanyl-lipoteichoic acid: role of diglyceride kinase in the synthesis of phosphatidylglycerol for chain elongation. J. Bacteriol. 154:1110–16 117. Theilacker C, Kaczynski Z, Kropec A, Fabretti F, Sange T, et al. 2006. Opsonic antibodies to Enterococcus faecalis strain 12030 are directed against lipoteichoic acid. Infec. Immun. 74:5703–12 118. Theilacker C, Kropec A, Hammer F, Sava I, Wobser D, et al. 2012. Protection against Staphylococcus aureus by antibody to the polyglycerolphosphate backbone of heterologous lipoteichoic acid. J. Infect. Dis. 205:1076–85 119. Tillett WS, Goebel WF, Avery OT. 1930. Chemical and immunological properties of a species-specific carbohydrate of pneumococci. J. Exp. Med. 52:895–900 120. Tomasz A. 1967. Choline in the cell wall of a bacterium: novel type of polymer-linked choline in Pneumococcus. Science 157:694–97 121. Tomasz A. 1968. Biological consequences of the replacement of choline by ethanolamine in the cell wall of Pneumococcus: chain formation, loss of transformability, and loss of autolysis. Proc. Natl. Acad. Sci. USA 59:86–93 122. Tomasz A, Westphal M. 1971. Abnormal autolytic enzyme in a pneumococcus with altered teichoic acid composition. Proc. Natl. Acad. Sci. USA 68:2627–30 123. Uchikawa K, Sekikawa I, Azuma I. 1986. Structural studies on lipoteichoic acids from four Listeria strains. J. Bacteriol. 168:115–22 124. Volkman BF, Zhang Q, Debabov DV, Rivera E, Kresheck GC, Neuhaus FC. 2001. Biosynthesis of D-alanyl-lipoteichoic acid: the tertiary structure of apo-D-alanyl carrier protein. Biochemistry 40:7964–72 125. Vollmer W, Tomasz A. 2001. Identification of the teichoic acid phosphorylcholine esterase in Streptococcus pneumoniae. Mol. Microbiol. 39:1610–22 126. Voss S, Hallström T, Saleh M, Burchhardt G, Pribyl T, et al. 2013. The choline-binding protein PspC of Streptococcus pneumoniae interacts with the C-terminal heparin-binding domain of vitronectin. J. Biol. Chem. 288:15614–27 127. Weart RB, Lee AH, Chien AC, Haeusser DP, Hill NS, Levin PA. 2007. A metabolic sensor governing cell size in bacteria. Cell 130:335–47 128. Webb AJ, Karatsa-Dodgson M, Gründling A. 2009. Two-enzyme systems for glycolipid and polyglycerolphosphate lipoteichoic acid synthesis in Listeria monocytogenes. Mol. Microbiol. 74:299–314 129. Weisman LE, Thackray HM, Garcia-Prats JA, Nesin M, Schneider JH, et al. 2009. Phase 1/2 doubleblind, placebo-controlled, dose escalation, safety, and pharmacokinetic study of pagibaximab (BSYXA110), an antistaphylococcal monoclonal antibody for the prevention of staphylococcal bloodstream infections, in very-low-birth-weight neonates. Antimicrob. Agents Chemother. 53:2879–86 130. Weisman LE, Thackray HM, Steinhorn RH, Walsh WF, Lassiter HA, et al. 2011. A randomized study of a monoclonal antibody (pagibaximab) to prevent staphylococcal sepsis. Pediatrics 128:271–79 131. Wörmann ME, Corrigan RM, Simpson PJ, Matthews SJ, Gründling A. 2011. Enzymatic activities and functional interdependencies of Bacillus subtilis lipoteichoic acid synthesis enzymes. Mol. Microbiol. 79:566–83 132. Wörmann ME, Reichmann NT, Malone CL, Horswill AR, Gründling A. 2011. Proteolytic cleavage inactivates the Staphylococcus aureus lipoteichoic acid synthase. J. Bacteriol. 193:5279–91 www.annualreviews.org • Lipoteichoic Acid Synthesis Changes may still occur before final publication online and in print 99 MI68CH05-Grundling ARI 26 April 2014 15:26 Annu. Rev. Microbiol. 2014.68. Downloaded from www.annualreviews.org by Imperial College London on 06/17/14. For personal use only. 133. Yokoyama K, Araki Y, Ito E. 1988. The function of galactosyl phosphorylpolyprenol in biosynthesis of lipoteichoic acid in Bacillus coagulans. Eur. J. Biochem. 173:453–58 134. Yonus H, Neumann P, Zimmermann S, May JJ, Marahiel MA, Stubbs MT. 2008. Crystal structure of DltA: implications for the reaction mechanism of non-ribosomal peptide synthetase adenylation domains. J. Biol. Chem. 283:32484–91 135. Zhang JR, Idanpaan-Heikkila I, Fischer W, Tuomanen EI. 1999. Pneumococcal licD2 gene is involved in phosphorylcholine metabolism. Mol. Microbiol. 31:1477–88 100 Percy · Gründling Changes may still occur before final publication online and in print