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.

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.

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.

17.2 Purple Phototrophic Bacteria Carry out anoxygenic photosynthesis; no O2 evolved Contain bacteriochlorophylls and carotenoid pigments (Figure 17.3) Produce intracytoplasmic photosynthetic membranes with varying morphologies © 2012 Pearson Education, Inc.

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.

Figure 17.4 Figure 17.4 Membrane systems of phototrophic purple bacteria as revealed by the electron microscope. © 2012 Pearson Education, Inc.

17.2 Purple Phototrophic Bacteria Purple sulfur bacteria 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 © 2012 Pearson Education, Inc.

Figure 17.5 Figure 17.5 Bright-field and phase-contrast photomicrographs of purple sulfur bacteria. © 2012 Pearson Education, Inc.

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.

Figure 17.6 Figure 17.6 Blooms of purple sulfur bacteria. © 2012 Pearson Education, Inc.

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 photoheterotrophically using light as an energy source and organic compounds as a carbon source © 2012 Pearson Education, Inc.

Figure 17.7 Figure 17.7 Representatives of several genera of purple nonsulfur bacteria. © 2012 Pearson Education, Inc.

17.3 The Nitrifying Bacteria Able to grow chemolithotrophically at the expense of reduced inorganic nitrogen compounds Nitrification (oxidation of ammonia to nitrate) occurs as two separate reactions by different groups of bacteria Many species have internal membrane systems that house key enzymes in nitrification Highest numbers in habitats with large amounts of ammonia Most are obligate chemolithotrophs and aerobes © 2012 Pearson Education, Inc.

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.

17.4 Sulfur- and Iron-Oxidizing Bacteria Sulfur-oxidizing bacteria Grow chemolithotrophically on reduced sulfur compounds Some obligate chemolithotrophs possess special structures that house Calvin cycle enyzmes © 2012 Pearson Education, Inc.

Figure 17.9 Figure 17.9 Nonfilamentous sulfur chemolithotrophs. © 2012 Pearson Education, Inc.

Figure 17.10 Figure 17.10 Filamentous sulfur-oxidizing bacteria. © 2012 Pearson Education, Inc.

17.5 Hydrogen-Oxidizing Bacteria Most can grow autotrophically with H2 as sole electron donor and O2 as electron acceptor (“knallgas” reaction) Contain one or more hydrogenase enzymes that use H2 either to produce ATP or for reducing power for autotrophic growth © 2012 Pearson Education, Inc.

Figure 17.13 Figure 17.13 Hydrogen bacteria. © 2012 Pearson Education, Inc.

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 Contain extensive internal membrane systems for methane oxidation © 2012 Pearson Education, Inc.

Figure 17.14 Figure 17.14 Methanotrophs. © 2012 Pearson Education, Inc.

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.

Figure 17.16 Figure 17.16 Typical pseudomonad colonies and cell morphology of pseudomonads. © 2012 Pearson Education, Inc.

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.

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.

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.

Figure 17.17 Figure 17.17 Colonies of Acetobacter aceti on calcium carbonate (CaCO3) agar containing ethanol as electron donor. © 2012 Pearson Education, Inc.

17.10 Neisseria Neisseria and their relatives can be isolated from animals, and some species of this group are pathogenic N. gonorrheae and N. meningitidis Some of the most naturally competent bacteria known © 2012 Pearson Education, Inc.

Figure 17.21 Figure 17.21 Chromobacterium and Neisseria. © 2012 Pearson Education, Inc.

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.

Figure 17.22 Figure 17.22 Butanediol producer. © 2012 Pearson Education, Inc.

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.

17.11 Enteric Bacteria Salmonella and Shigella Closely related to Escherichia Usually pathogenic Salmonella characterized immunologically by surface antigens © 2012 Pearson Education, Inc.

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.

Figure 17.24 Figure 17.24 Swarming in Proteus. © 2012 Pearson Education, Inc.

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.

Figure 17.26 Figure 17.26 Bioluminescent bacteria and their role as light organ symbionts in the flashlight fish. © 2012 Pearson Education, Inc.

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.

Figure 17.27 Figure 17.27 Rickettsias growing within host cells. © 2012 Pearson Education, Inc.

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.

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.

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.

Figure 17.31 Figure 17.31 Attack on a prey cell by Bdellovibrio. © 2012 Pearson Education, Inc.

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 17.32 Developmental cycle of the bacterial predator Bdellovibrio bacteriovorus. Bdelloplast Prey periplasmic space Penetration © 2012 Pearson Education, Inc.

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.

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 17.36 Cell division in different bacteria. 4. Polar growth without differentiation of cell size: Rhodopseudomonas, Nitrobacter, Methylosinus © 2012 Pearson Education, Inc.