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Bacteria: The Proteobacteria
Chapter 17 Bacteria: The Proteobacteria
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I. The Phylogeny of Bacteria
17.1 Phylogenetic Overview of Bacteria © 2012 Pearson Education, Inc.
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Figure 17.1 Deferribacter Cytophaga Flavobacteria Spirochetes Planctomyces/ Pirellula Verrucomicrobiaceae Green sulfur bacteria Deinococci Green nonsulfur bacteria Chlamydia Cyanobacteria Thermotoga Actinobacteria Gram-positive bacteria Firmicutes and Mollicutes Thermodesulfobacterium Figure 17.1 Some major phyla of Bacteria based on 16S ribosomal RNA gene sequence comparisons. Nitrospira Aquifex See Figure 17.2 Proteobacteria © 2012 Pearson Education, Inc.
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17.1 Phylogenetic Overview of Bacteria
Proteobacteria (Figure 17.2) A major lineage (phyla) of Bacteria Includes many of the most commonly encountered bacteria Most metabolically diverse of all Bacteria Chemolithotrophy, chemoorganotrophy, phototrophy Morphologically diverse Divided into five classes Alpha-, Beta-, Delta-, Gamma-, Epsilon- © 2012 Pearson Education, Inc.
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Proteobacterial Classes
Figure 17.2 16S rRNA Gene Tree of Proteobacteria Proteobacterial Classes Bacillus Nitrosococcus Thermochromatium Acidithiobacillus Beggiatoa Gamma Pseudomonas Vibrio Escherichia Methylobacter Gallionella Nitrosomonas Methylophilus Derxia Ralstonia Beta Spirillum Rhodocyclus Thiobacillus Neisseria Methylobacterium Nitrobacter Rhodopseudomonas Beijerinckia Alpha Paracoccus Azotobacter Rickettsia Acetobacter Mariprofundus Zeta Campylobacter Figure 17.2 Phylogenetic tree of some key genera of Proteobacteria. Sulfurimonas Epsilon Thiovulum Wolinella Desulfosarcina Desulfovibrio Delta Myxococcus Nitrospina Major metabolisms Chemolithotrophy Anoxygenic phototrophy Sulfur compounds (H2S, S0, etc.) Methylotrophy Ferrous iron (Fe2) Sulfate reduction Ammonia (NH3) or nitrite (NO2) Nitrogen fixation Hydrogen (H2) © 2012 Pearson Education, Inc.
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II. Phototrophic, Chemolithotrophic, and Methanotrophic Proteobacteria
17.2 Purple Phototrophic Bacteria 17.3 The Nitrifying Bacteria 17.4 Sulfur- and Iron-Oxidizing Bacteria 17.5 Hydrogen-Oxidizing Bacteria 17.6 Methanotrophs and Methylotrophs © 2012 Pearson Education, Inc.
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17.2 Purple Phototrophic Bacteria
Carry out anoxygenic photosynthesis; no O2 evolved Morphologically diverse group Genera fall within the Alpha-, Beta-, or Gammaproteobacteria Contain bacteriochlorophylls and carotenoid pigments (Figure 17.3) Produce intracytoplasmic photosynthetic membranes with varying morphologies (Figure 17.4) © 2012 Pearson Education, Inc.
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Figure 17.3 Figure 17.3 Photograph of liquid cultures of phototrophic purple bacteria showing the color of species with various carotenoid pigments. © 2012 Pearson Education, Inc.
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Figure 17.4 Figure 17.4 Membrane systems of phototrophic purple bacteria as revealed by the electron microscope. © 2012 Pearson Education, Inc.
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17.2 Purple Phototrophic Bacteria
Purple sulfur bacteria (Figure 17.5) Use hydrogen sulfide (H2S) as an electron donor for CO2 reduction in photosynthesis Sulfide oxidized to elemental sulfur (S0) that is stored as globules either inside or outside cells Sulfur later disappears as it is oxidized to sulfate (SO42) © 2012 Pearson Education, Inc.
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Figure 17.5 Figure 17.5 Bright-field and phase-contrast photomicrographs of purple sulfur bacteria. © 2012 Pearson Education, Inc.
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17.2 Purple Phototrophic Bacteria
Purple sulfur bacteria (cont’d) Many can also use other reduced sulfur compounds, such as thiosulfate (S2O32) All are Gammaproteobacteria Found in illuminated anoxic zones of lakes and other aquatic habitats where H2S accumulates, as well as sulfur springs (Figure 17.6) © 2012 Pearson Education, Inc.
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Figure 17.6 Figure 17.6 Blooms of purple sulfur bacteria.
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17.2 Purple Phototrophic Bacteria
Purple nonsulfur bacteria (Figure 17.7) Organisms able to use sulfide as an electron donor for CO2 reduction Most can grow aerobically in the dark as chemoorganotrophs Some can also grow anaerobically in the dark using fermentation or anaerobic respiration Most can grow photoheterotrophically using light as an energy source and organic compounds as a carbon source All in Alpha- and Betaproteobacteria © 2012 Pearson Education, Inc.
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Figure 17.7 Figure 17.7 Representatives of several genera of purple nonsulfur bacteria. © 2012 Pearson Education, Inc.
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17.3 The Nitrifying Bacteria
Able to grow chemolithotrophically at the expense of reduced inorganic nitrogen compounds Found in Alpha-, Beta-, Gamma-, and Deltaproteobacteria © 2012 Pearson Education, Inc.
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17.3 The Nitrifying Bacteria
Nitrifying bacteria (cont’d) Nitrification (oxidation of ammonia to nitrate) occurs as two separate reactions by different groups of bacteria Ammonia oxidizers (nitrosifiers; e.g., Nitrosococcus; Figure 17.8a) Nitrite oxidizer (e.g., Nitrobacter; Figure 17.8b) © 2012 Pearson Education, Inc.
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Reaction: Reaction: NH3 1 O2 NO2 H2O NO2 O2 NO3 1 2 1 2
Figure 17.8 Reaction: 2 1 NH3 1 O2 NO2 H2O Figure 17.8 Nitrifying bacteria. Reaction: 2 1 NO2 O2 NO3 © 2012 Pearson Education, Inc.
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17.3 The Nitrifying Bacteria
Nitrifying bacteria (cont’d) Many species have internal membrane systems that house key enzymes in nitrification Ammonia monooxygenase: oxidizes NH3 to NH2OH Nitrite oxidase: oxidizes NO2 to NO3 Widespread in soil and water © 2012 Pearson Education, Inc.
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17.3 The Nitrifying Bacteria
Nitrifying bacteria (cont’d) Highest numbers in habitats with large amounts of ammonia Examples: sites with extensive protein decomposition and sewage treatment facilities Most are obligate chemolithotrophs and aerobes One exception is annamox organisms, which oxidize ammonia anaerobically © 2012 Pearson Education, Inc.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria Grow chemolithotrophically on reduced sulfur compounds Two broad classes: Neutrophiles Acidophiles Some acidophiles able to use ferrous iron (Fe2+) © 2012 Pearson Education, Inc.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria (cont’d) Thiobacillus and close relatives are most studied Rod-shaped Sulfur compounds most commonly used as electron donors are H2S, S0, S2O32; generates sulfuric acid Achromatium Common in freshwater sediments Spherical cells © 2012 Pearson Education, Inc.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria (cont’d) Some obligate chemolithotrophs possess special structures that house Calvin cycle enyzmes (carboxysomes; Figure 17.9) © 2012 Pearson Education, Inc.
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Figure 17.9 Figure 17.9 Nonfilamentous sulfur chemolithotrophs.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria (cont’d) Beggiatoa (Figure 17.10) Filamentous, gliding bacteria Found in habitats rich in H2S Examples: sulfur springs, decaying seaweed beds, mud layers of lakes, sewage-polluted waters, and hydrothermal vents Most grow mixotrophically with reduced sulfur compounds as electron donors and organic compounds as carbon sources © 2012 Pearson Education, Inc.
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Figure 17.10 Figure 17.10 Filamentous sulfur-oxidizing bacteria.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria (cont’d) Thioploca (Figure 17.11) Large, filamentous sulfur-oxidizing bacteria that form cell bundles surrounded by a common sheath Thick mats found on ocean floor off Chile and Peru Couple anoxic oxidation of H2S with reduction of NO3 to NH4+ © 2012 Pearson Education, Inc.
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Figure 17.11 Figure 17.11 Cells of a large marine Thioploca species.
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17.4 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-oxidizing bacteria (cont’d) Thiothrix (Figure 17.12) Filamentous sulfur-oxidizing bacteria in which filaments group together at their ends by a holdfast to form cellular arrangements called rosettes Obligate aerobic mixotrophs © 2012 Pearson Education, Inc.
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Figure 17.12 Figure Thiothrix. © 2012 Pearson Education, Inc.
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17.5 Hydrogen-Oxidizing Bacteria
Most can grow autotrophically with H2 as sole electron donor and O2 as electron acceptor (“knallgas” reaction) Both gram-negative and gram-positive representatives Contain one or more hydrogenase enzymes that use H2 either to produce ATP or for reducing power for autotrophic growth © 2012 Pearson Education, Inc.
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17.5 Hydrogen-Oxidizing Bacteria
Hydrogen-oxidizing bacteria (cont’d) Most are facultative chemolithotrophs and can grow chemoorganotrophically (Figure 17.13) Some can grow on carbon monoxide (CO) as electron donor (carboxydotrophs) © 2012 Pearson Education, Inc.
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Figure 17.13 Figure 17.13 Hydrogen bacteria.
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17.6 Methanotrophs and Methylotrophs
Use CH4 and a few other one-carbon (C1) compounds as electron donors and source of carbon Widespread in soil and water Obligate aerobes Morphologically diverse © 2012 Pearson Education, Inc.
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17.6 Methanotrophs and Methylotrophs
Organisms that can grow using carbon compounds that lack C-C bonds Most are also methanotrophs © 2012 Pearson Education, Inc.
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17.6 Methanotrophs and Methylotrophs
C1 methanotrophs Methanotrophs contain methane monooxygenase Incorporates an atom of oxygen from O2 into methane to produce methanol Methanotrophs contain large amounts of sterols © 2012 Pearson Education, Inc.
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17.6 Methanotrophs and Methylotrophs
Classification of Methanotrophs Two major groups: Type I Type II Contain extensive internal membrane systems for methane oxidation © 2012 Pearson Education, Inc.
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17.6 Methanotrophs and Methylotrophs
Type I methanotrophs (Figure 17.14) Assimilate C1 compounds via the ribulose monophosphate cycle Gammaproteobacteria Membranes arranged as bundles of disc-shaped vesicles Lack complete citric acid cycle Obligate methylotrophs © 2012 Pearson Education, Inc.
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17.6 Methanotrophs and Methylotrophs
Type II methanotrophs (Figure 17.14) Assimilate C1 compounds via the serine pathway Alphaproteobacteria Paired membranes that run along periphery of cell © 2012 Pearson Education, Inc.
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Figure 17.14 Figure 17.14 Methanotrophs.
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17.6 Methanotrophs and Methylotrophs
Ecology and Isolation of Methanotrophs Widespread in aquatic and terrestrial environments Methane monooxygenase also oxidizes ammonia; competitive interaction between substrates Certain marine mussels have symbiotic relationships with methanotrophs (Figure 17.15) © 2012 Pearson Education, Inc.
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Figure 17.15 Figure 17.15 Methanotrophic symbionts of marine mussels.
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III. Aerobic and Facultatively Aerobic Chemoorganotrophic Proteobacteria
Pseudomonas and the Pseudomonads Acetic Acid Bacteria Free-Living Aerobic Nitrogen-Fixing Bacteria 17.10 Neisseria, Chromobacterium, and Relatives 17.11 Enteric Bacteria 17.12 Vibrio, Aliivibrio, and Photobacterium 17.13 Rickettsias © 2012 Pearson Education, Inc.
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17.7 Pseudomonas and the Pseudomonads
All genera within the pseudomonad group are Straight or curved rods with polar flagella Chemoorganotrophs Obligate aerobes Species of the genus Pseudomonas and related genera can be defined on the basis of phylogeny and physiological characteristics © 2012 Pearson Education, Inc.
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Figure 17.16 Figure Typical pseudomonad colonies and cell morphology of pseudomonads. © 2012 Pearson Education, Inc.
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17.7 Pseudomonas and the Pseudomonads
Nutritionally versatile Ecologically important organisms in water and soil Some species are pathogenic Includes human opportunistic pathogens and plant pathogens © 2012 Pearson Education, Inc.
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17.7 Pseudomonas and the Pseudomonads
Zymomonas Genus of large, gram-negative rods that carry out vigorous fermentation of sugars to ethanol Used in production of fermented beverages © 2012 Pearson Education, Inc.
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17.8 Acetic Acid Bacteria Acetic acid bacteria
Organisms that carry out complete oxidation of alcohols and sugars Leads to the accumulation of organic acids as end products Motile rods Aerobic High tolerance to acidic conditions © 2012 Pearson Education, Inc.
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17.8 Acetic Acid Bacteria Acetic acid bacteria (cont’d)
Commonly found in alcoholic juices Used in production of vinegar Some can synthesize cellulose Colonies can be identified on CaCO3 agar plates containing ethanol © 2012 Pearson Education, Inc.
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Figure 17.17 Figure Colonies of Acetobacter aceti on calcium carbonate (CaCO3) agar containing ethanol as electron donor. © 2012 Pearson Education, Inc.
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17.9 Free-Living Aerobic Nitrogen-Fixing Bacteria
Major genera capable of fixing N2 nonsymbiotically are Azotobacter, Azospirillum, and Beijerinckia Azotobacter are large, obligately aerobic rods (Figure 17.18) Can form resting structures (cysts) All genera produce extensive capsules or slime layers (Figure 17.19) Believed to be important in protecting nitrogenase from O2 © 2012 Pearson Education, Inc.
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Figure 17.18 Figure 17.18 Azotobacter vinelandii.
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Figure 17.19 Figure Examples of slime production by free-living N2-fixing bacteria. © 2012 Pearson Education, Inc.
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17.9 Free-Living Aerobic Nitrogen-Fixing Bacteria
Additional genera of free-living N2 fixers include acid-tolerant microbes Examples: Azomonas and Derxia (Figure 17.20) © 2012 Pearson Education, Inc.
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Bipolar lipid bodies Figure 17.20
Figure Phase-contrast photomicrographs of two genera of acid-tolerant, free-living N2-fixing bacteria. © 2012 Pearson Education, Inc.
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17.10 Neisseria, Chromobacterium, and Relatives
Neisseria, Chromobacterium, and their relatives can be isolated from animals, and some species of this group are pathogenic (Figure 17.21) © 2012 Pearson Education, Inc.
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Figure 17.21 Figure 17.21 Chromobacterium and Neisseria.
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17.11 Enteric Bacteria Enteric bacteria (Figure 17.22)
Phylogenetic group within the Gammaproteobacteria Facultative aerobes Motile or nonmotile, nonsporulating rods Possess relatively simple nutritional requirements Ferment sugars to a variety of end products © 2012 Pearson Education, Inc.
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Figure 17.22 Figure 17.22 Butanediol producer.
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17.11 Enteric Bacteria Enteric bacteria can be separated into two broad groups by the type and proportion of fermentation products generated by anaerobic fermentation of glucose (Figure 17.23) Mixed-acid fermenters 2,3-butanediol fermenters © 2012 Pearson Education, Inc.
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Figure 17.23 Glycolysis Glucose Pyruvate Lactate Uninoculated tube CO2 Succinate Ethanol Acetyl CoA Acid gas reaction (H2 CO2) Acetate CO2 Formate H2 Gas collection tube Mixed-acid fermentation (for example, Escherichia coli) Glucose Glycolysis 2,3-Butanediol CO2 Pyruvate Ethanol Figure Enteric fermentations. Lactate Succinate Weak acid strong gas reaction Acetate CO2 H2 Butanediol color reaction Butanediol fermentation (for example, Enterobacter aerogenes) © 2012 Pearson Education, Inc.
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17.11 Enteric Bacteria Escherichia
Universal inhabitants of intestinal tract of humans and warm-blooded animals Synthesize vitamins for host Some strains are pathogenic © 2012 Pearson Education, Inc.
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17.11 Enteric Bacteria Salmonella and Shigella
Closely related to Escherichia Usually pathogenic Salmonella characterized immunologically by surface antigens © 2012 Pearson Education, Inc.
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17.11 Enteric Bacteria Proteus
Genus containing rapidly motile cells; capable of swarming (Figure 17.24) Frequent cause of urinary tract infections in humans © 2012 Pearson Education, Inc.
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Figure 17.24 Figure 17.24 Swarming in Proteus.
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17.11 Enteric Bacteria Butanediol fermenters are a closely related group of organisms Some capable of pigment production (Figure 17.25) © 2012 Pearson Education, Inc.
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Figure 17.25 Figure 17.25 Colonies of Serratia marcescens.
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17.12 Vibrio, Aliivibrio, and Photobacterium
The Vibrio group Cells are motile, straight or curved rods Facultative aerobes Fermentative metabolism Best-known genera are Vibrio, Aliivibrio, and Photobacterium Most inhabit aquatic environments © 2012 Pearson Education, Inc.
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17.12 Vibrio, Aliivibrio, and Photobacterium
The Vibrio group (cont’d) Some are pathogenic Some are capable of light production (bioluminescence; Figure 17.26) Catalyzed by luciferase, an O2-dependent enzyme Regulation is mediated by population density (quorum sensing) © 2012 Pearson Education, Inc.
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Figure 17.26 Figure Bioluminescent bacteria and their role as light organ symbionts in the flashlight fish. © 2012 Pearson Education, Inc.
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17.13 Rickettsias Rickettsias (Figure 17.27)
Small, coccoid or rod-shaped cells Most are obligate intracellular parasites Causative agent of several human diseases © 2012 Pearson Education, Inc.
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Figure 17.27 Figure 17.27 Rickettsias growing within host cells.
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17.13 Rickettsias Wolbachia (Figure 17.28)
Genus of rod-shaped Alphaproteobacteria Intracellular parasites of arthropod insects Affect the reproductive fitness of hosts © 2012 Pearson Education, Inc.
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Figure 17.28 Figure Wolbachia. © 2012 Pearson Education, Inc.
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IV. Morphologically Unusual Proteobacteria
17.14 Spirilla 17.15 Sheathed Proteobacteria: Sphaerotilus and Leptothrix 17.16 Budding and Prosthecate/Stalked Bacteria © 2012 Pearson Education, Inc.
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17.14 Spirilla Spirilla (Figure 17.29)
Group of motile, spiral-shaped Proteobacteria Key taxonomic features include Cell shape and size Number of polar flagella Metabolism Physiology Ecology © 2012 Pearson Education, Inc.
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Figure 17.29 Figure Spirilla. © 2012 Pearson Education, Inc.
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17.14 Spirilla Spirilla A few are magnetotactic, demonstrating directed movement in a magnetic field (Figure 17.30) © 2012 Pearson Education, Inc.
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Flagellum Figure 17.30 Figure 17.30 A magnetotactic spirillum.
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17.14 Spirilla Spirilla Bdellovibrio
Prey on other bacteria (Figure 17.31) Two stages of penetration (Figure 17.32) Obligate aerobes Members of Deltaproteobacteria Widespread in soil and water, including marine environments © 2012 Pearson Education, Inc.
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Figure 17.31 Figure 17.31 Attack on a prey cell by Bdellovibrio.
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Figure 17.32 Release of progeny Prey lysis (2.5–4 h postattachment)
Bdellovibrio Prey cytoplasm Elongation of Bdellovibrio inside the bdelloplast Prey Attachment 40–60 min 5–20 min Figure Developmental cycle of the bacterial predator Bdellovibrio bacteriovorus. Bdelloplast Prey periplasmic space Penetration © 2012 Pearson Education, Inc.
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17.15 Sheathed Proteobacteria: Sphaerotilus & Leptothrix
Sheathed Bacteria Filamentous Betaproteobacteria Unique life cycle in which flagellated swarmer cells form within a long tube or sheath Under unfavorable conditions, swarmer cells move out to explore new environments Common in freshwater habitats rich in organic matter © 2012 Pearson Education, Inc.
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17.15 Sheathed Proteobacteria: Sphaerotilus & Leptothrix
Sphaerotilus (Figure 17.33) Nutritionally versatile Able to use simple organic compounds Obligate aerobes Cells within the sheath divide by binary fission Eventually swarmer cells are liberated from sheaths © 2012 Pearson Education, Inc.
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Figure 17.33 Figure 17.33 Sphaerotilus natans.
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17.15 Sheathed Proteobacteria: Sphaerotilus & Leptothrix
Sphaerotilus and Leptothrix are able to precipitate iron oxides (Figure 17.34) © 2012 Pearson Education, Inc.
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Figure 17.34 Figure 17.34 Leptothrix and iron precipitation.
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17.16 Budding and Prosthecate/Stalked Bacteria
Large and heterogeneous group Primarily Alphaproteobacteria Form various kinds of cytoplasmic extrusions bounded by a cell wall (collectively called prosthecae; Figure 17.35) Cell division different from other bacteria (Figure 17.36) © 2012 Pearson Education, Inc.
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Figure 17.35 Holdfast Prosthecae Flagellum Swarmer cell
Figure Prosthecate bacteria. © 2012 Pearson Education, Inc.
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Equal products of cell division:
Figure 17.36 I. Equal products of cell division: Binary fission: most bacteria II. Unequal products of cell division: 1. Simple budding: Pirellula, Blastobacter 2. Budding from Hyphae: Hyphomicrobium, Rhodomicrobium, Pedomicrobium 3. Cell division of stalked organism: Caulobacter Figure Cell division in different bacteria. 4. Polar growth without differentiation of cell size: Rhodopseudomonas, Nitrobacter, Methylosinus © 2012 Pearson Education, Inc.
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17.16 Budding and Prosthecate/Stalked Bacteria
Budding Bacteria Divide as a result of unequal cell growth (Figure 17.37) Two well-studied genera: Hyphomicrobium (chemoorganotrophic; Figure 17.38) Rhodomicrobium (phototrophic © 2012 Pearson Education, Inc.
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Figure 17.37 Figure 17.37 Stages in the Hyphomicrobium cell cycle.
DNA Mother cell Hypha Hypha lengthens; DNA replication Copy of chromosome enters bud Chromosome Bud Formation of cross-septum Septum Figure Stages in the Hyphomicrobium cell cycle. Motile swarmer maturates and swims away DNA in mother cell replicates again Cell separation Flagellum Hypha lengthens further © 2012 Pearson Education, Inc.
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Hypha Mother cell Figure 17.38
Figure Morphology of Hyphomicrobium. Hypha Mother cell © 2012 Pearson Education, Inc.
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17.16 Budding and Prosthecate/Stalked Bacteria
Prosthecate and Stalked Bacteria (Figure 17.39) Appendaged bacteria that attach to particulate matter, plant material, and other microbes in aquatic environments Appendages increase surface-to-volume ratio of the cells © 2012 Pearson Education, Inc.
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Stalk Holdfast Stalk Figure 17.39 Figure 17.39 Stalked bacteria.
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17.16 Budding and Prosthecate/Stalked Bacteria
Caulobacter Chemoorganotroph Produces a cytoplasm-filled stalk Often seen on surfaces in aquatic environments with stalks of several cells attached to form rosettes Holdfast structure present on the end of the stalk used for attachment Model system for cell division and development (Figure 17.40) © 2012 Pearson Education, Inc.
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Stalk elongation DNA synthesis Cross- band formation Cell division
Figure 17.40 Stalk elongation DNA synthesis Cross- band formation Cell division Initiation of DNA synthesis Synthesis of flagellin Loss of flagellum Figure Growth of Caulobacter. Elongated stalked cell Swarmer cell Stalked cell Predivisional cell 10 20 30 40 50 60 70 80 90 Time (min) © 2012 Pearson Education, Inc.
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17.16 Budding and Prosthecate/Stalked Bacteria
Gallionella Chemolithotrophic iron-oxidizing bacteria Possess twisted stalk-like structure composed of ferric hydroxide (Figure 17.41) Common in waters draining bogs, iron springs, and other environments rich in Fe2+ © 2012 Pearson Education, Inc.
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Figure 17.41 Figure The neutrophilic ferrous iron oxidizer, Gallionella ferruginea, from an iron seep near Ithaca, New York. © 2012 Pearson Education, Inc.
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V. Delta- and Epsilonproteobacteria
17.17 Myxobacteria 17.18 Sulfate- and Sulfur-Reducing Proteobacteria 17.19 The Epsilonproteobacteria © 2012 Pearson Education, Inc.
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17.17 Myxobacteria Gliding Gliding Bacteria
A form of motility exhibited by some bacteria Gliding Bacteria Are typically either long rods or filaments Lack flagella, but can move when in contact with surfaces © 2012 Pearson Education, Inc.
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17.17 Myxobacteria Myxobacteria
Group of gliding bacteria that form multicellular structures (fruiting bodies) and show complex developmental life cycles Deltaproteobacteria Chemoorganotrophic soil bacteria Lifestyle includes consumption of dead organic matter or other bacterial cells © 2012 Pearson Education, Inc.
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17.17 Myxobacteria Fruiting myxobacteria exhibit complex behavioral patterns and life cycles Vegetative cells are simple, nonflagellated rods that glide across surfaces (Figure 17.42) Obtain nutrients by lysing other bacteria and utilizing released nutrients Under appropriate conditions, vegetative cells aggregate, construct fruiting bodies, and undergo differentiation into myxospores (Figure 17.43) © 2012 Pearson Education, Inc.
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Figure 17.42 Figure Myxococcus. © 2012 Pearson Education, Inc.
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Figure 17.43 Figure 17.43 Stigmatella aurantiaca.
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Myxobacteria The life cycle of fruiting myxobacterium is complex (Figure 17.45) © 2012 Pearson Education, Inc.
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Fruiting-body and myxospore formation
Figure 17.45 Fruiting-body and myxospore formation Mound of cells Fruiting body Myxospores Swarming and aggregation Chemical induction Germination Figure Life cycle of Myxococcus xanthus. Vegetative cycle Outgrowth of vegetative cells © 2012 Pearson Education, Inc.
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17.18 Sulfate- and Sulfur-Reducing Proteobacteria
Dissimilative sulfate- and sulfur-reducing bacteria Over 40 genera of Deltaproteobacteria Use SO42 and S0 as electron acceptors, and organic compounds or H2 as electron donors H2S is an end product Most obligate anaerobes Widespread in aquatic and terrestrial environments © 2012 Pearson Education, Inc.
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17.18 Sulfate- and Sulfur-Reducing Proteobacteria
Physiology of sulfate-reducing bacteria Group I Include Desulfovibrio, Desulfomonas, Desulfotomaculum, and Desulfobulbus (Figure 17.48) Oxidize lactate, pyruvate, or ethanol to acetate Group II Include Desulfobacter, Desulfococcus, Desulfosarcina, and Desulfonema (Figure 17.48) Oxidize fatty acids, lactate, succinate, and benzoate to CO2 © 2012 Pearson Education, Inc.
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Figure 17.48a Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48b Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48c Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48d Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48e Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48f Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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Figure 17.48g Figure Representative sulfate-reducing and sulfur-reducing bacteria. © 2012 Pearson Education, Inc.
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17.19 The Epsilonproteobacteria
Abundant in oxic–anoxic interfaces in sulfur-rich environments Example: hydrothermal vents Many are autotrophs Use H2, formate, sulfide, or thiosulfate as electron donor © 2012 Pearson Education, Inc.
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17.19 The Epsilonproteobacteria
Pathogenic and nonpathogenic representatives Campylobacter and Helicobacter (pathogenic) Arcobacter (pathogenic) Sulfurospirillum and Thiovulum (nonpathogenic) Wolinella succinogenes (found in rumen) © 2012 Pearson Education, Inc.
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