Download 16.3 Cell-Wall-Less Gram

Brock Biology of
Microorganisms
Twelfth Edition
Madigan / Martinko
Chapter 16
Dunlap / Clark
Bacteria: Gram-Positive and Other Bacteria
Lectures by Buchan & LeCleir
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I. Overview of Gram-Positive and Other Bacteria
 Bacteria has many other phyla, including
 Gram-positive bacteria
 Large group of mostly chemoorganotrophic
 Cyanobacteria
 Oxygeneic phototrophs that have evolutionary roots near those of grampositive bacteria
 Phylogenetically early-branching phyla
 Such as Aquifex
 Other morphologically distinct groups
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II. Gram-Positive Bacteria and Actinobacteria
 16.1 Nonsporulating Gram-Positive Bacteria
 16.2 Endospore-Forming Gram-Positive Bacteria
 16.3 Cell-Wall-Less Gram-Positive Bacteria: The
Mycoplasmas
 16.4 Actinobacteria: Coryneform and Propionic Acid
Bacteria
 16.5 Actinobacteria: Mycobacterium
 16.6 Filamentous Actinobacteria: Streptomyces and
Relatives
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II. Gram-Positive Bacteria and Actinobacteria
 Gram-positive bacteria are a large and diverse
group
 Previously divided into two groups
 High G+C (Actinobacteria), >50% G+C
 Low G+C <50% G+C
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16.1 Nonsporulating Gram-Positive Bacteria
 Key genera: Staphylococcus, Micrococcus,
Streptococcus, Lactobacillus, Sarcina
 Staphylococcus and Micrococcus
 Aerobic, cocci
 Resistant to reduced water potential
 Tolerate high salt
 Many species are pigmented
 Staphylococcus aureus
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16.1 Nonsporulating Gram-Positive Bacteria
 Sarcina
 Obligate anaerobes
 Extremely acid tolerant
 Can inhabit and grow in stomachs of monogastric
animals
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16.1 Nonsporulating Gram-Positive Bacteria
 Streptococcus
 Homofermentative
 Play important roles in production of buttermilk, silage,
and other products
 Some species are pathogenic
 Lactococcus: genera of dairy significance
 Enterococcus: genera of fecal origin
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16.1 Nonsporulating Gram-Positive Bacteria
 Lactobacillus
 Rod-shaped
 Common in dairy products
 Resistant to acidic conditions
 Grow in pH as low as 4
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16.1 Nonsporulating Gram-Positive Bacteria
 Listeria
 Gram-positive coccobacilli
 Form chains 3–5 cells long
 Require full oxic or microoxic conditions for growth
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Distinguishing Features of Major Gram-Positive Cocci
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Staphylococcus aureus
Figure 16.1
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Sarcina
Figure 16.2
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Differentiation of the Principal Genera of Lactic Acid Bacteria
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Gram-Positive Cocci
Lactococcus lactis
Streptococcus sp.
Figure 16.3
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Differential Characteristics
Complete hemolysis (β-hemolysis): due to hemolysins (e.g. streptolysin O or S).
Antigenic groups are divided based on the presence of specific carbohydrate antigens.
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Lactobacillus species
Lactobacillus acidophilus
Lactobacillus brevis
Lactobacillus delbrueckii
Figure 16.4
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16.2 Endospore-Forming Gram-Positive Bacteria
 Key Genera: Bacillus, Clostridium, Sporosarcina,
Heliobacterium
 Distinguished on the basis of cell morphology, shape
and cellular position of endospore
 Generally found in soils
 Endospores are advantageous for soil microorganisms
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Major Genera of Endospore-Forming Bacteria
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16.2 Endospore-Forming Gram-Positive Bacteria
 Bacillus and Paenibacillus
 Many produce extracellular hydrolytic enzymes that
break down polymers
 Many bacilli produce antibiotics
 Paenibacillus popilliae and Bacillus thuringiensis
produce insect larvicides
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Characteristics of Representative Species of Bacilli
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Toxic Parasporal Crystal in Bacillus thuringiensis
Figure 16.6
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16.2 Endospore-Forming Gram-Positive Bacteria
 Clostridium
 Lack a respiratory chain, anaerobic
 Some Clostridia perform Stickland reactions
 Metabolism of pair of amino acids
 Mainly found in anaerobic pockets in the soil
 Also live in mammalian intestinal tract
 Some are pathogenic; cause diseases such as botulism,
tetanus, and gas gangrene
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Characteristics of Some Groups of Clostridia
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Clostridium Species and Endospore Location
Clostridium cadaveris
Terminal endospores
Clostridium sporogenes
Subterminal endospores
Clostridium bifermentans
Central endspores
Figure 16.5
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16.2 Endospore-Forming Gram-Positive Bacteria
 Sporosarcina
 Unique among endospore formers because cells are
cocci instead of rods
 Strictly aerobic, spherical cells
 Common in soils
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Sporsarcina ureae
Figure 16.7
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16.2 Endospore-Forming Gram-Positive Bacteria
 Heliobacteria
 Phototrophic gram-positive bacteria
 Anoxygenic phototrophs
 Produce bacteriochlorophyll g
 Strict anaerobes
 Reside in soils and also in highly alkaline environments
(i.e., soda lakes and alkaline soils)
 Have nitrogen-fixation capabilities
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Cells and Endospores of Heliobacteria
Heliobacillus mobilis
Heliophilum fasciatum
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Heliobacterium
gestii
Figure 16.8
16.3 Cell-Wall-Less Gram-Positive Bacteria: Mycoplasmas
 Key genera: Mycoplasma, Spiroplasma
 Lack cell walls
 Some of the smallest organisms capable of autonomous
growth
 Parasites that inhabit animal and plant hosts
 Key components of peptidoglycan are missing
- Muramic acid and diaminopimelic acid
 Mycoplasma cells are pleomorphic
 Cells may be cocci or filaments of various lengths
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Major Characteristics of Mycoplasmas
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16.3 Cell-Wall-Less Gram-Positive Bacteria: Mycoplasmas
 Spiroplasma
 Helical or spiral-shaped wall-less cells
 Rotary screw motility
 Isolated from ticks, hemolymph and gut of insects,
vascular plant fluids, and insects that feed on the fluids
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Mycoplasma mycoides
Figure 16.9
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“Fried Egg” Appearance of Mycoplasma Colonies on Agar
Dense central core
Figure 16.10
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Spiroplasma from Hemolymph of D. pseudoobscura
“Sex ratio” spiroplasma
Figure 16.11
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16.4 Actinobacteria: Coryneform & Propionic Acid Bacteria
 Key genera: Corynebacterium, Arthrobacter,
Propionibacterium
 Actinobacteria form their own phylum
- High G+C gram-positive bacteria
 Over 30 taxonomic families
 Rod to filamentous, usually aerobic
 Mostly harmless commensals (Mycobacterium are notable
exceptions)
 Valuable for antibiotics and certain fermented dairy products
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16.4 Actinobacteria: Coryneform & Propionic Acid Bacteria
 Corynebacterium
 Gram-positive, aerobic, non-motile, rod-shaped
 Form club-shaped, irregular-shaped, or V-shaped cell
arrangements
 Extremely diverse
 Arthrobacter
 Primarily soil organisms
 Remarkably resistant to dessication and starvation
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16.4 Actinobacteria: Coryneform & Propionic Acid Bacteria
 Propionic Acid Bacteria
 First discovered in Swiss cheese
 Gram-positive anaerobes
 Have metabolic strategy called secondary fermentation
 Obtain energy from fermentation products produced
by other bacteria
- Propionibacterium: lactic acid
- Propionigenium: succinate
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Snapping Division in Arthrobacter crystallopoietes
Figure 16.12
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Cell Division in Arthrobacter crystallopoietes
Figure 16.13
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Stages in Life Cycle of Arthrobacter globiformis
Rods to coccoid forms
Figure 6.14
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16.5 Actinobacteria: Mycobacterium
 Mycobacterium
 Rod-shaped organisms, exhibit acid-fastness
 First discovered by Robert Koch
 Not readily stained by Gram stain because of high
surface lipid content
 Cells are somewhat pleomorphic
 Separated into two groups: slow and fast growers
 Classified into three groups based on pigmentation
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Acid-Fast Stain (Ziehl-Neelsen Stain)
Basic fuchsin and phenol – heating – washing (DW) – acid alcohol –wash – methylene blue
- Acid-fast organism: red
- Non-acid-fast organism: blue
Figure 16.15
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Characteristic Colony Morphology of Mycobacteria
M. tuberculosis colony
Colony of virulent M. tuberculosis
at an early stage
M. avium colonies
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Figure 16.16
Structure of Cord Factor, a Mycobacterial Glycolipid
6,6’-dimycolyltrehalose
Figure 16.17
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16.6 Filamentous Actinobacteria: Streptomyces & Others
 Key genera: Streptomyces, Actinomyces
 Filamentous, gram-positive bacteria
 Produce mycelium analogous to mycelium of filamentous
fungi
 Over 500 species of Streptomyces are recognized
 Streptomyces spores are called conidia (in the aerial
mycelium sporophores)
 Primarily soil microorganisms, responsible for earthy odor of
soil (geosmins)
 Strict aerobes that produce many extracellular enzymes
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16.6 Filamentous Actinobacteria: Streptomyces & Others
 Streptomyces
 50% of all isolated Streptomyces produce antibiotics
 Over 500 distinct antibiotics produced by Streptomyces
 Some produce more than one antibiotic
 Genomes are typically quite large (8 Mbp and larger)
 Knowledge of the ecology of Streptomyces remains poor
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Nocardia
Figure 16.18
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Spore-Bearing Structures of Actinomycetes
Streptomyces sp.
Streptomyces sp.
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Figure 16.19
Spore Formation in Streptomyces
Figure 16.20
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Colonies of Streptomyces
Figure 16.22
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Antibiotics from Streptomyces
Streptomyces coelicolor and red-colored
antibiotic undecylprodigiosin
Figure 16.23
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Some Common Antibiotics Synthesized by Streptomyces
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III. Cyanobacteria and Prochlorophytes
 16.7 Cyanobacteria
 16.8 Prochlorophytes
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16.7 Cyanobacteria
 Key genera: Synechococcus, Oscillatoria, Nostoc
 Oxygenic phototrophs
 Impressive morphological diversity
 Unicellular (divide by binary fission)
 Unicellular (divide by multiple fission)
 Filamentous (with heterocysts)
 Filamentous (nonheterocystous)
 Branching filamentous
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Genera and Grouping of Cyanobacteria
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Cyanobacteria: the Five Major Morphologies
Gloeothece
Dermocarpa
Oscillatoria
Figure 16.24a-c
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Cyanobacteria: the Five Major Morphologies
Anabaena
Fischerella
Figure 16.24d-e
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16.7 Cyanobacteria
 Most species are obligate phototrophs
- chlorophyll a and phycobilins
( Red algae also has chlorophyll a and phycobilin)
 Many cyanobacteria produce potent neurotoxins
 Widely distributed in terrestrial, freshwater, and marine
habitats
 Can be phototrophic component of lichens
 Often form extensive crusts in desert soils
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Thylakoids in Cyanobacteria
Synecoccus lividus
Figure 16.25
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Thylakoids in Cyanobacteria
Figure 16.25
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16.7 Cyanobacteria
 Gas vesicles are found in many cyanobacteria
 Help maintain buoyancy
 Keep cell in water column where there is light
 Heterocysts are rounded, enlarged cells
 Anoxic environment inside heterocyst
 Site for nitrogen fixation
 Nitrogenase is sensitive to oxygen
 Lack photosystem II and low in phycobilin pigments
 Unable to fix CO2
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16.7 Cyanobacteria
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16.7 Cyanobacteria
 Cyanophycin
 A copolymer of Asp and Arg
 Nnitrogen storage product
 Also an energy reserve
- arginine dihydrolase system (arginine deiminase, ornithine
carbamoyl transferase, and carbamate kinase)
* Arg + H2O → citrulline + NH3
citrulline + Pi → ornithine + carbomoyl phosphate
carbomoyl phosphate + ADP → ATP + NH3 + CO2
(Net: Arg + ADP + Pi + H2O → ornithine +2NH3 + CO2 + ATP)
 Many cyanobacteria display gliding motility
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16.7 Cyanobacteria
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16.8 Prochlorophytes
 Key genera: Prochloron, Prochlorothrix, and
Prochlorococcus
 Oxygenic phototrophs
 Prochloron was first prochlorophyte discovered
- contains chlorophylls a and b
- No phycobilins
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Electron Micrograph of the Prochlorophyte Prochloron
Prochloron
Figure 16.28
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16.8 Prochlorophytes
 Prochlorothrix
 Have chlorophylls a and b and lacks phycobilins
 Prochlorococcus
 Found in euphotic zone of the open oceans
 The smallest and most abundant photosynthetic
microorganism on Earth (?)
 0.5–0.8 micrometers in diameter
 105 Prochlorococcus per milliliter of seawater
 Produce divinyl chlorophyll a (not the true chlorophyll a),
chlorophyll b, and alpha-carotene
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Filamentous Prochlorothrix and Acaryochloris
Contain chlorophyll a and b
Phase Contrast
Electron Micrograph
of Thin Section
Acaryochlorus,
Thin Section
Prochlorothrix
Figure 16.29
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IV. Chlamydia
 16.9 The Chlamydia
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16.9 The Chlamydia
 Key genera: Chlamydia, Chlamydophila
 Obligately parasitic with poor metabolic capacities
 One of the simplest biochemical capacities of all known
bacteria
 Currently a cause of one of the leading sexually
transmitted diseases
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16.9 The Chlamydia
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16.9 The Chlamydia
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Chlamydia
Chlamydia psittaci
Figure 16.30
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The Infection Cycle of Chlamydia
Figure 16.31a
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The Infection Cycle of Chlamydia
Human Chlamydial Infection
Figure 16.31b
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V. Planctomyces/ Pirellula
 16.10 Planctomyces/Pirellula: A phylogenetically
unique stalked bacterium
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16.10 Planctomyces: A Phylogenetically Unique Bacterium
 Key genera: Planctomyces, Pirellula, Gemmata
 Planctomyces is a budding bacterium
 Facultative aerobic chemoorganotroph
 Stalked
 Primarily aquatic
 Extensive cell compartmentalization including a
membrane-enclosed nuclear structure
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Planctomyces maris
Figure 16.32
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Gemmata: a Nucleated Bacterium
Figure 16.33
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VI. The Verrucomicrobia
 16.11 Verrucomicrobium and Prosthecobacter
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16.11 Verrucomicrobium and Prosthecobacter
 Key genera: Verrucomicrobium
 Form cytoplasmic extensions called prosthecae
 Produce two prosthecae per cell
 Aerobic to facultative aerobic bacteria
 Inhabit freshwater and marine environments as well
as forest and agricultural soils
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Verrucomicrobium spinosum
Figure 16.34
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VII. The Flavobacteria
 16.12 Bacteroides and Flavobacterium
 16.13 Acidobacteria
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16.12 Bacteroides and Flavobacterium
 Key genera: Bacteroides, Flavobacterium
 Bacteroides
 Obligately anaerobic
 Numerically dominant bacterium in human intestinal tract
 Synthesize sphingolipids, which are normally found in
mammalian tissues
 Flavobacteria
 Found primarily in aquatic environments
 Aerobic, nutritionally restricted, frequently yellow-pigmented
 Other genera are psychrophilic (i.e., Polaribacter)
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Sphingolipids
A number of compounds
Glycerol
Sphingosine
Carboxy group of fatty acid
Figure 16.35
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16.13 Acidobacteria
 Key genera: Acidobacterium, Geothrix, Holophaga
 Gram-negative chemoorganotrophs
 Abundant in soils, freshwater habitats, hot spring
microbial mats, wastewater treatment reactors, and
sewage sludge
 16S rRNA gene evidence of up to 6 major groups
 Most are still uncultured
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VIII. The Cytophaga Group
 16.14 Cytophaga and Relatives
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16.14 Cytophaga and Relatives
 Key genera: Cytophaga, Flexibacter, Rhodothermus
and Salinibacter
 Long, slender gram-negative rods
 Move by gliding
 Many Cytophaga digest polysaccharides such as
cellulose or chitin
 Some are fish pathogens
 Cytophaga and Sporocytophaga are obligately aerobic and
probably account for much of the oxic cellulose digestion
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Cytophaga and Sporocytophaga
Streak of Cytophaga Species
Hydrolyzing Agar in Petri Dish
Colonies of Sporocytophaga
Growing on Cellulose
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Figure 16.36a-b
Cytophaga and Sporocytophaga
Cytophaga hutchinsonii
Sporocytophaga
myxococcoides
Figure 16.36c-d
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16.14 Cytophaga and Relatives
 Flexibacter differs from Cytophaga because they require
complex media for growth and are not cellulolytic
 Common in freshwater saprophytes and soils
 None have been identified as pathogenic
 Rhodothermus and Salinibacter
 Gram-negative, red or yellow pigmented, obligately aerobic
 Salinibacter is the most salt tolerant of all Bacteria
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IX. Green Sulfur Bacteria
 16.15 Chlorobium and Other Green Sulfur Bacteria
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16.15 Chlorobium and Other Green Sulfur Bacteria
 Key genera: Chlorobium, Chlorobaculum, Prosthecochloris,
Chlorochromatium
 Green sulfur bacteria are phylogenetically distinct, non-motile,
anoxygenic phototrophs
 Bacteriochlorophyll a + either bacteriochlorophylls c, d, or e
 Utilize H2S as an electron donor and oxidize it to SO42 Autotrophy is supported using a reversal in the citric acid cycle
 Have chlorosomes: oblong bacteriochlorophyll-rich bodies
bounded by a thin membrane (a lipid monolayer)
 Green- and brown-colored species exist
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Green and Brown Chlorobia
Chlorobaculum tepidum
Chlorobaculum phaeobacteroides
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Phototrophic Green Sulfur Bacteria
Chlorobium limicola
Chlorobium clathratiforme
Figure 16.37
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Chlorobaculum tepidum
Chlorosome
Chlorobaculum tepidum: a thermophilic green sulfur bacterium
Figure 16.38
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Chlorobaculum tepidum
chlorosomes
Figure 16.38
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Genera and Characteristics of Green Sulfur Bacteria
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16.15 Chlorobium and Other Green Sulfur Bacteria
 Green sulfur bacteria inhabit anoxic environments
rich in H2S
 Some green sulfur bacteria form consortia
 Involves the green sulfur bacterium and
a chemoorganotrophic bacterium
 Phototrophic member is called epibiont
 Epibiont is physically attached to nonphototrophic cell
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16.15 Chlorobium and Other Green Sulfur Bacteria
Chlorochromatium aggregatum
Differential
contrast
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DAPI-stained
Stained with
phylogenetic
probe
16.16 Spirochetes
 Key genera: Spirochaeta, Treponema, Cristispira,
Leptospira, Borrelia
 Gram-negative, motile, and tightly coiled
 Widespread in aquatic environments and in animals
 Have endoflagella: located in the periplasm of the cell
 Classified into 8 genera based on habitat, pathogenicity,
phylogeny, and morphological and physiological
characteristics
 Also found in the rumen of animals
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Morphology of Spirochetes
Same magnification
Spirochaeta
stenostrepta
Spirochaeta plicatilis
Figure 16.41
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Motility in Spirochetes
Figure 16.42
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16.16 Spirochetes
 Spirochaeta
 Free-living, anaerobic and facultatively anaerobic spirochetes
 Cristispira
 Found in nature, primarily in the crystalline style of mollusks
 No Cristipara have yet been cultured
 Treponema
 Anaerobic host-associated spirochetes that are commensal
or parasites of humans
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16.16 Spirochetes
 Borrelia
 Majority are human or animal pathogens
 Borrelia burgdorferi is the causative agent of Lyme disease
 B. burgdorferi has a linear chromosome
 Leptospira and Leptonema
 Strictly anaerobic spirochetes
 Rodents are the natural host of Leptospira
 Cause of leptospirosis in humans
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Cristispira
Figure 16.44
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Treponema and Borrelia
Regularly coiled
Irregularly coiled
Treponema saccharophilum
Borrelia burgdorferii
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Figure 16.44
XI. Deinococci
 16.17 Deinococcus and Thermus
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16.17 Deinococcus and Thermus
 Thermus
 Thermophilic, aerobic, organotrophic
 Source of Taq DNA polymerase
 Deinococcus
 Gram-positive, aerobic, organotrophic
 Most are red or pink due to carotenoids
 Resist UV radiation, gamma radiation, and desiccation
 Resistant to most mutagenic agents
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The Radiation-Resistant Coccus Deinococcus radiodurans
Outer membrane layer
Nucleoid
Figure 16.45
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XII. The Green Nonsulfur Bacteria
 16.18 Chloroflexus and Relatives
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16.18 Chloroflexus and Relatives
 Key genera: Chloroflexus, Heliothrix, Roseiflexus
 Chloroflexus
 Thermophilic filamentous bacteria
 Form thick microbial mats in neutral to alkaline hot
springs
 Grows best phototrophically, can grow
photoautotrophically
 Bacteriochlorophylls a and c
 Has chlosomes
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16.18 Chloroflexus and Relatives
 Thermomicrobium
 Chemotrophic, strictly aerobic, gram-negative rod
 Grow optimally in complex media at 75oC
 Membrane lipids
- Have 1,2-dialcohols (instead of glycerol)
- Have neither ester nor ether linkage
 Lack peptidoglycan
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The Unusual Lipids of Thermomicrobium
13-methyl-1,2-nonadecaediol of Thermomicrobium roseum
Fatty acid
Fatty acid
Phosphate
Phosphate
Bilayer membrane
Figure 16.46
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Green Nonsulfur Bacteria
Chloroflexus
aurantiacus
Oscillochloris sp.
Chloronema sp.
Right: C. Aurantiacus
Left: Roseiflexus sp.
Figure 16.47
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XIII. Hyperthermophilic Bacteria
 16.19 Thermotoga and Thermodesulfobacterium
 16.20 Aquifex, Thermocrinis, and Relatives
 Hyperthermophile: optimal temperature is > 80oC
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16.19 Thermotoga and Thermodesulfobacterium
 Key genera: Thermotoga, Thermodesulfobacterium
 Thermotoga
 Rod-shaped, hyperthermophile (can grow at 90°C)
 Anaerobic, fermentative, chemoorganotroph
 20% of genes likely originated from Archaea (contains many
genes that show strong homology to genes from
hyperthermophilic Archaea)
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Hyperthermophilic Bacteria
Thermotoga maritima (temperature optimum: 80oC)
Aquifex pyrophilus (temperature optimum: 85oC)
Figure 16.48
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16.19 Thermotoga and Thermodesulfobacterium
 Thermodesulfobacterium
 Thermophilic (temp. opt. 70oC), sulfate-reducing bacterium
 Strict anaerobe
 Unable to utilize acetate as electron donor
 Lipids
- Ether-linked (instead of ester-linked)
- Contain C17 hydrocarbon along with some fatty acids
(instead of phytanyl, the polyisoprenoid C20 hydrocarbon in
Archaea)
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Thermodesulfobacterium
Figure 16.49
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16.20 Aquifex, Thermocrinis, and Relatives
 Key genera: Aquifex and Thermocrinis
 Aquifex
 Obligately chemolithotrophic hyperthermophile
- H2, So, and S2O32- as electron donors
- O2 or NO3- as electron acceptors
- Reverse TCA cycle for CO2 fixation
 Most thermophilic of all Bacteria
- Opt. temp. 85°C, max. temp. 95°C
 1.55 Mbp genome
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Hyperthermophilic Bacteria
Thermotoga maritima (temperature optimum: 80oC)
Aquifex pyrophilus (temperature optimum: 85oC)
Figure 16.48
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16.20 Aquifex, Thermocrinis, and Relatives
 Thermocrinis
 Chemolithotrophic hyperthermophile
- H2, So, and S2O32- as electron donors
- O2 as electron acceptor
- Reverse TCA cycle for CO2 fixation
 Opt. temp. 80°C
 Grow as filamentous pink “streamers” in nature
- In static culture: grow as individual rod-shaped cells
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Thermocrinis ruber
85°C outflow, Yellow
Stone National Park
Figure 16.50
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XIV. Nitrospira and Deferribacter
 16.21 Nitrospira, Deferribacter, and Relatives
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16.21 Nitrospira, Deferribacter, and Relatives
 Key genera: Nitrospira, Deferribacter
 Relatively little is known about these organisms
 Chemolithotrophs or chemoorganotrophs
 Thermophiles or mesophiles
 Identified by ribosomal RNA sequencing
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16.21 Nitrospira, Deferribacter, and Relatives
 Nitrospira group
 Nitrospira
- Chemolithotroph: NO2- as an electron donor
- Horizontal transfer of genes involved in nitrification from
nitrifying Proteobacteria to Nitrospira? (or vice versa?)
- Most of nitrite oxdized in nature is probably due to the
activities of Nitrospira (∵ Nitrospira is much more common
than Nitrobacter in nature )
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16.21 Nitrospira, Deferribacter, and Relatives
 Nitrospira group
 Leptospirillum
- Iron-oxidizing chemolithotroph
- Responsible for much of the acid mine drainage
 Thermodesulfovibrio
- Thermophilic sulfate-reducing bacterium
- inhabits hot spring microbial mats
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16.21 Nitrospira, Deferribacter, and Relatives
 Deferribacter group
 Deferribacter
- Obligately anaerobic
- Anaerobic respiration with a variety of electron acceptors (e.g.
Fe3+ and Mn4+ )
 Geovibrio
- Obligately anaerobic
- Anaerobic respiration with a variety of electron acceptors
(e.g. Fe3+ and Mn4+ )
 Flexistipes
- Obligately anaerobic, fermentative
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