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Chapter 19 The Deinococci and Nonproteobacteria Gram Negatives Domain Phylum Class Order Family Genus Species Domain Bacteria - volumes 1 and 5 of Bergey’s manual of systematic bacteriology - Deinococci and nonproteobacteria gram negatives *gram-negative bacteria not belonging to phylum Proteobacterium - characteristics include * morphology, reproduction, physiology, metabolism, and ecology Figure 19.1 Aquificae and Thermotogae Aquificae Aquificae - thought to be deepest (oldest) branch of Bacteria - contains one class, one order, and five genera *two best studied genera are Aquifex and Hydrogenobacter - Bacterial thermophiles * optimum growth temperatures above 85°C Genus Aquifex - gram-negative rod - thermophile **growth optimum 85°C - maximum 95°C - microaerophilic - chemolithoautotroph *uses hydrogen, thiosulfite, and sulfur as electron donor *uses oxygen as electron acceptor * genome ~1/3 size of E. coli Phylum Thermotogae - second deepest branch of Bacteria - contains one class, one order, and six genera * best studied genus is Thermotoga Genus Thermotoga - gram-negative rods * have outer sheathlike envelope that can balloon out from ends of cell - thermophiles * optimum 80°C; maximum 90°C * grow in active geothermal areas ( e.g., marine hydrothermal vents and terrestrial solfataric springs ) Thermotoga… - chemoheterotrophs * have functional glycolytic pathway * can grow anaerobically on carbohydrates and proteins digests * ~24% of coding sequences are similar to archaeal genes ( may be due to horizontal gene transfer) Figure 19.2 Deinococcus-Thermus - contains one class, Deinococci - two orders, Deinococcales and Thermales - three genera # genus Deinococcus is best studied * 9 of 11 species are mesophilic * 2 are thermophilic Deinococcus-Thermus - 2 - spherical or rod-shaped * associated in pairs or tetrads *stain gram positive but do not have typical gram-positive cell wall # layered outer membrane similar to gram negatives # L-ornithine in peptidoglycan # lacks teichoic acid * plasma membrane has large amounts of palmitoleic acid rather than phosphatidylglycerol phospholipids Figure 19.3 Deinococcus-Thermus - 3 - aerobic * catalase positive - produce acids from only a few sugars - extraordinarily resistant to desiccation and radiation * can survive 3–5 million rad (100 rad lethal to humans) - isolated from ground meat, feces, air, fresh water, and other sources, but natural habitat unknown Deinococcus-Thermus - 4 - genome consists of two circular chromosomes, a megaplasmid, and a small plasmid * radiation resistance due to ability to repair genome when it is severely damaged * efficient proteins (protected by manganese) and enzymes for DNA repair - within 12–24 hours can repair chromosomes fragmented by exposure to radiation Heterocyte - specialized cells used for nitrogen fixation * produced when organism is nitrogen deprived * differentiate from individual cells in filament # involves reorganization of photosynthetic membranes * thick heterocyst wall prevents O2 diffusion into heterocyst which would inactivate nitrogenase, enzyme responsible for nitrogen fixation Phylum Chlamydiae - gram negative - obligate intracellular parasites * must grow and reproduce inside host cells *although known for ability to cause disease, many grow within hosts such as protists, and animal cells without adverse effects - one class, one order, four families, six genera * genus Chlamydia is best studied Genus Chlamydia - nonmotile, coccoid, gram negative *cell walls lack muramic acid, peptidoglycan * have very small genomes - obligate intracellular parasites with unique developmental cycle *elementary body (EB) attaches to host cell *reticulate body (RB) reproduction by binary fission * differentiate back into EB, lyses cell Figure 19.12 Chlamydial Metabolism - cannot catabolize carbohydrates - cannot synthesize ATP or NAD+ * import up from host *do have genes for substrate-level phosphorylation, electron transport, and oxidative phosphorylation - RBs have biosynthetic capabilities when supplied precursors from host; can synthesize some amino acids - EBs seem to be dormant forms Phylum Spirochaetes - contains one class; one order, three families, 13 genera - gram negative, chemoheterotrophic bacteria with distinctive structure and motility * slender, long with flexible helical shape *creeping (crawling) motility due to a structure called an axial filament - oxygen requirements vary Table 19.3 Figure 19.13 Spirochaetes Motility - axial filament lies inside outer sheath * rotate, causing corkscrew-shaped outer sheath to rotate and move cell through surrounding liquid - motility adapted to moving through viscous solutions Figure 19.14 Figure 19.15 Symbiotic Associations between Spirochetes and Other Organisms - ecologically diverse free living symbiotic * hindguts of termites *digestive tracts of mollusks and mammals *oral cavities of animals disease *Lyme disease and syphilis are spirochete diseases Phylum Bacteroidetes - very diverse - contains three classes Bacteroides Flavobacteria Sphingobacteria - 12 families, and 63 genera Class Bacteroides - anaerobic, gram-negative rods, various shapes *do not form endospores *motile or nonmotile - chemoheterotrophs - fermentative - often found in oral cavity and intestinal tract of humans and other animals and the rumen of ruminants *often benefit host by degrading complex carbohydrates, providing extra nutrition to host *constitute up to 30% of bacteria from human feces * some cause disease