Bacteria: The Proteobacteria

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1 Bacteria: The Proteobacteria
Chapter 17

2 The Phylogeny of Bacteria
I. Phylum Proteobacteria

3 The Phylogeny of Bacteria – Major phyla of domain Bacteria
Phylogenetic Overview of Bacteria

4 Phylum Proteobacteria
A major lineage (phyla) of Bacteria Includes many of the most commonly encountered bacteria Most metabolically diverse of all domain Bacteria E.g., chemolithotrophy, chemoorganotrophy, phototrophy Morphologically diverse Divided into five classes Alpha-, Beta-, Delta-, Gamma-, Epsilon-

5 Major Genera of Proteobacteria

6 II Phototrophic, Chemolithotrophic & Methanotrophic
Proteobacteria 1. Purple Phototrophic Bacteria 2. The Nitrifying Bacteria 3. Sulfur- and Iron-Oxidizing Bacteria 4. Hydrogen-Oxidizing Bacteria 5. Methanotrophs and Methylotrophs

7 1. 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 Produce intracytoplasmic photosynthetic membranes with varying morphologies

8 Liquid Cultures of Phototrophic Purple Bacteria
Figure 15.2

9 Membrane Systems of Phototrophic Purple Bacteria
Figure 15.3

10 Purple Phototrophic Bacteria
Purple Sulfur Bacteria Use hydrogen sulfide (H2S) as an electron donor for CO2 reduction in photosynthesis Sulfide oxidized to elemental sulfur (So) that is stored as globules either inside or outside cells Sulfur later disappears as it is oxidized to sulfate (SO42-)

11 Photomicrographs of Purple Sulfur Bacteria
Figure 15.4

12 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

13 Genera and Characteristics of Purple Sulfur Bacteria

14 Genera and Characteristics of Purple Sulfur Bacteria

15 Genera and Characteristics of Purple Sulfur Bacteria

16 Blooms of Purple Sulfur Bacteria
Figure 15.5

17 Purple Non-sulfur Bacteria
Originally thought organisms were unable to use sulfide as an electron donor for CO2 reduction, now know most can Most can grow aerobically in the dark as chemoorganotrophs Some can also grow anaerobically in the dark using fermentative 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

18 Representatives of Purple Nonsulfur Bacteria
Figure 15.6

19 Genera and Characteristics of Purple Nonsulfur Bacteria

20 Genera and Characteristics of Purple Nonsulfur Bacteria

21 2. The Nitrifying Bacteria
Able to grow chemolithotrophically at the expense of reduced inorganic nitrogen compounds Found in Alpha-, Beta-, Gamma-, and Deltaproteobacteria Nitrification (oxidation of ammonia to nitrate) occurs as two separate reactions by different groups of bacteria Ammonia oxidizers (nitrosifyers) (e.g., Nitrosococcus) Nitrite oxidizer (nitrifyer) (e.g., Nitrobacter) Many species have internal membrane systems that house key enzymes in nitrification Ammonia monooxygenase: oxidizes NH3 to NH2OH Nitrite oxidase: oxidizes NO2- to NO3-

22 Nitrifying Bacteria (cont’d)
Widespread in soil and water Highest numbers in habitats with large amounts of ammonia i.e., sites with extensive protein decomposition and sewage treatment facilities Most are obligate chemolithotrophs and aerobes One exception is annamox organisms, which oxidize ammonia anaerobically

23 Figure 15.7

24 As carbon dioxide rises, food quality will decline without careful nitrogen management

25

26 3. Sulfur- and Iron-Oxidizing Bacteria
Sulfur-Oxidizing Bacteria Grow chemolithotrophically on reduced sulfur cmpds Two broad classes Neutrophiles Acidophiles (some also use ferrous iron (Fe2+) Thiobacillus (rods) Sulfur compounds most commonly used as electron donors are H2S, So, S2O32-; generates sulfuric acid Achromatium (spherical cells) Common in freshwater sediments Some obligate chemolithotrophs possess special structures that house Calvin cycle enyzmes (carboxysomes)

27 Beggiatoa Filamentous, gliding bacteria Found in habitats rich in H2S e.g., 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 Thioploca 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+

28 Non-filamentous Sulfur Chemolithotrophs
Filamentous Sulfur-Oxidizing Bacteria Figure 15.9

29 Sulfur- and Iron-Oxidizing Bacteria
Sulfur-Oxidizing Bacteria (cont’d) Thiothrix Filamentous sulfur-oxidizing bacteria in which filaments group together at their ends by a holdfast to form cellular arrangements called rosettes Obligate aerobic mixotrophs

30 Thiothrix Figure 15.12

31 4. 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 known Contain one or more hydrogenase enzymes that function to bind H2 and use it to either produce ATP or for reducing power for autotrophic growth Most are facultative chemolithotrophs and can grow chemoorganotrophically Some can grow on carbon monoxide (CO) as electron donor (carboxydotrophs)

32 Hydrogen Bacteria Figure 15.13

33 Characteristics of Common Hydrogen-Oxidizing Bacteria

34 5. Methanotrophs and Methylotrophs
Organisms that can grow using carbon compounds that lack C-C bonds [(CH3)2N (trimethylamine)HCOO- (formate), CH3OCOO CH3 (Dimethyl carbonate), (CH3)2SO (dimethyl sulfoxide), CH3OH (methanol), CH3NH2 (methylamine), CH3)2NH (dimethylamine)] Most are also methanotrophs – use CH4 Methanotrophs Use CH4and a few other one-carbon (C1) compounds as electron donors and source of carbon Widespread in soil and water Obligate aerobes Morphologically diverse

35 5. Methanotrophs and Methylotrophs
Methanotrophs (cont'd) Methanotrophs methane monooxygenase Which incorporates an atom of oxygen from O2 into methane to produce methanol Methanotrophs contain large amounts of sterols Classification of Methanotrophs Two major groups: Type I Type II Contain extensive internal membrane systems for methane oxidation

36 5. Methanotrophs and Methylotrophs
Type I Methanotrophs Assimilate C1 compounds via the ribulose monophosphate cycle Gammaproteobacteria Membranes arranged as bundles of disc-shaped vesicles Lack complete citric acid cycle Obligate methylotrophs Type II Methanotrophs Assimilate C1 compounds via the serine pathway Alphaproteobacteria Paired membranes that run along periphery of cell

37 Electron Micrographs of Methanotrophs
Type I membrane system Methylococcus capsulatans (β-Proteobacteria) Carbon asimilation pathwy: ribulose monophosphate pathway Type II membrane system Methylosinus (α Proteobacteria) Carbon assimilation pathway: serine Lookup the metabolic pathways for Methylomonas methanica (type II) and Methylococcus capsulatans (type 1) in KEGG ( Figure 15.14

38 Some Characteristics of Methanotrophic Bacteria

39 5. 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

40 III Aerobic & Facultatively Aerobic Chemoorganotrophic
Proteobacteria 1. Pseudomonads including Pseudomonas 2. Acetic Acid Bacteria 3. Free-Living Aerobic Nitrogen-Fixing Bacteria 4. Neisseria, Chromobacterium, & Relatives 5. Enteric Bacteria 6. Vibrio, Alivibrio, and Photobacterium 7. Rickettsias

41 1. Pseudomonads including Pseudomonas
Key Genera: Pseudomonas Burkholderia Zymomonas Xanthomonas All genera are: Straight or curved rods with polar flagella Stain gram negative Chemoorganotrophs Obligate aerobes Posses polar flagella Phylogenetically, the group is scattered within the Proteobacteria

42 Typical Pseudomonad Colonies – eg Burkholderia cepacia
Lophotrichous polar flagella Figure 15.16a Figure 15.16b

43 1. Pseudomonads including Pseudomonas
Members of the genus Pseudomonas and related genera can be defined on the basis of phylogeny and physiological characteristics Nutritionally versatile Ecologically important organisms in water and soil Some species are pathogenic Includes human opportunistic pathogens and plant pathogens Refer to the next two slides for an over view

44 Subgroups and Characteristics of Pseudomonads

45 Pathogenic Pseudomonads

46 Genus Zymomonas Genus of large, gram-negative rods that carry out vigorous fermentation of sugars to ethanol Used in production of fermented beverages

47 2. Acetic Acid Bacteria Organisms that carry out complete oxidation of alcohols & sugars Leads to the accumulation of organic acids as end products Motile rods Aerobic High tolerance to acidic conditions Commonly found in alcoholic juices Used in production of vinegar Some can synthesize cellulose Colonies can be identified on CaCO3 agar plates containing ethanol

48 3. Free-Living Aerobic Nitrogen-Fixing Bacteria
A variety of soil microbes are capable of fixing N2 aerobically Distributed in alpha, beta and gamma Proteobacteria The major genera of bacteria capable of fixing N2 nonsymbiotically are Azotobacter, Azospirillium, and Beijerinckia Azotobacter are large, obligately aerobic rods; can form resting structures (cysts) All genera produce extensive capsules or slime layers; believed to be important in protecting nitrogenase from O2 (nitrogenase is oxygen-sensitive)

49 Azotobacter vinelandii
Cells (2 um) Cysts (3 um) Azotobacter vinelandii Figure 15.18

50 Slime producing Nitrogen2-fixing Bacteria
Beijerinckia species produce colonies with abundant slime Cells of Derixia gummosa encased in slime Slime producing Nitrogen2-fixing Bacteria Figure 15.19a

51 Beijerinckia indica (PHB is present)
Derixia gummosa Beijerinckia indica (PHB is present) Acid-tolerant, free-living N2 fixing bacteria live in acid soils

52

53

54

55 4. Neisseria, Chromobacterium, and Relatives
Neisseria, Chromobacterium, and their relatives can be isolated from animals, and some species of this group are pathogenic. N. gonorrhoeae – gonorrhea N. meningitidis – fatal inflammation of brain membrane 4. Neisseria, Chromobacterium, and Relatives

56 Characteristics of the Genera of Gram-Negative Cocci

57 Chromobacterium violaceum – produces violacein, a purple pigment
Structure of the aromatic compoun, violacein Colony showing purple colour Figure 15.21a

58 5. Enteric Bacteria (Fam. Enterobacteriaceae)
Relatively homogeneous phylogenetic group within the Gammaproteobacteria Facultative aerobes Motile or non-motile, nonsporulating rods Possess relatively simple nutritional requirements Ferment sugars to a variety of end products Enteric bacteria can be separated into two broad groups by the type and proportion of fermentation products generated by anaerobic fermentation of glucose Mixed-acid fermentators 2,3-butanediol fermentators

59 Enteric Fermentations
Figure 15.23a

60 Diagnostic tests and differential media are often used to identify various genera of enteric bacteria

61 Key Diagnostic Reactions Used to Separate Enteric Bacteria

62 Key Diagnostic Reactions Used to Separate Enteric Bacteria

63 A Simple Key to the Main Genera of Enteric Bacteria
Figure 15.24

64 Escherichia Universal inhabitants of intestinal tract of humans and warm-blooded animals Synthesize vitamins for host Some strains are pathogenic – cause health problems Enteropathogenic (EPEC) – surface K antigens allows attachment & colonisation Enterhemorrhagic (EHEC) – food / water, O157:H7 (O = CW, somatic, LPS; H = flagella proteins)

65 Salmonella and Shigella
Closely related to Escherichia (DDH > 50 & 70% respectively) Usually pathogenic S. typhi - typhoid Salmonella is characterized immunologically by 3 surface antigens: (used for tracking epidemics) O antigens H antigens Vi antigens, outer polysaccharide layer; typing S. typhi

66 Proteus Genus containing rapidly motile cells; capable of swarming
Frequent cause of urinary tract infections in humans

67 Butanediol fermentators – Enterobacter, Klebsiella & Serratia are a closely related group of organisms Serratia produces secondary metabolite, prodigiosin, a red pigment isolated from water, soil, insect / vertebrate guts, human intestine. S. marcescens: human pathogen infections from medical procedures contaminant in intravenous fluids

68 Reactions Used to Separate 2,3-Butanediol Producers

69 6. Vibrio, Alivibrio, and Photobacterium
The Vibrio Group Cells are motile, straight or curved rods Facultative aerobes Possess a fermentative metabolism Best known genera are Vibrio, Alivibrio & Photobacterium Most inhabit aquatic environments Some are pathogenic Some are capable of light production (bioluminescence) Catalyzed by luciferase, an O2-dependent enzyme Regulation is mediated by population density (quorum sensing)

70 Bacterial Bioluminescence
Light emission Most are marine isolates (Vibrio, Alivibrio, Photobacterium) but some terrestrial May colonise specialized light organs of some maring fish & squids or on dead skin of crustacean / fish V. cholera & V. vulnificus are pathogens; care when handling luminous bacteria Bioluminescence only when oxygen is present LuxCDABE gene products, luciferase, oxygen and a population density response (acyl homoserine [AHL], quorum sensing) is required

71 Bioluminescent Bacteria as Light Organ Symbionts
Figure 15.27c Figure 15.27f Figure 15.27a

72 7. Rickettsias Rickettsias Small, coccoid or rod-shaped cells
Mostly obligate intracellular parasites; small genome size Cannot grow outside a host cell; do not survive long outside the host Causative agent of several human diseases Typical procaryotic cell structure 7. Rickettsias

73 Small 0. 3um cells in tissue culture (a). EM of R
Small 0.3um cells in tissue culture (a). EM of R. popilliae growing in a vacuole in the host beetle, Melolontha melolontha (b) Figure 15.28a Figure 15.28b

74 Characteristics of Rickettsias

75 Wolbachia Genus of rod-shaped Alphaproteobacteria
Intracellular parasites of arthropod insects Affect the reproductive fitness of hosts

76 IV Morphologically Unusual Proteobacteria
1. Spirilla 2. Sheathed Proteobacteria: Sphaerotilus & Leptothrix 3. Budding and Prosthecate/Stalked Bacteria

77 1. Spirilla Group of motile, spiral-shaped Proteobacteria:
Spirillum & relatives Magentospirillum Bdellovibrio Key taxonomic features include Cell shape and size Number of polar flagella Metabolism Physiology Ecology

78 Spirilla : Spirillum Volutans
Figure 15.30a

79 Magnetotactic Spirilla
Highly motile Isolated from freshwater habitats Magnetotactic movement – directed by magnetic field Fe304 magentosome & Fe3S4 (greigite)

80 Bdevellovibrio (leech)
Prey on other bacteria Obligate aerobes Members of Deltaproteobacteria Widespread in soil and water, including marine environments Figure 15.33a

81 Developmental Cycle of Bdellevibrio Bacteriovorus
Figure 15.33b

82 Attachment and Penetration of a Prey Cell by Bdellevibrio
Figure 15.32a

83 2. 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

84 Sheathed Proteobacteria: Sphaerotilus & Leptothrix
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

85 Sphaerotilus Natans Figure 15.34a

86 Sphaerotilus Natans Figure 15.34b

87 Sphaerotilus Natans Figure 15.34c

88 Sheathed Proteobacteria: Sphaerotilus & Leptothrix
Sphaerotilus and Leptothrix are able to precipitate iron oxides

89 Leptothrix and Iron Precipitation
Figure 15.35

90 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)

91 Features of Stalked, Appendaged and Budding Bacteria

92 Prosthecate Bacteria Figure 15.36a

93 Prosthecate Bacteria Figure 15.36b

94 Prosthecate Bacteria Figure 15.36c

95 Cell Division Figure 15.37

96 Budding and Prosthecate/Stalked Bacteria
Budding Bacteria Divide as a result of unequal cell growth Two well-studied genera Hyphomicrobium (chemoorganotrophic) Rhodomicrobium (phototrophic)

97 Stages in the Hyphomicrobium Cell Cycle
Figure 15.38

98 Morphology of Hyphomicrobium
Figure 15.39a

99 Morphology of Hyphomicrobium
Figure 15.39b

100 Budding and Prosthecate/Stalked Bacteria
Prosthecate and Stalked Bacteria Appendaged bacteria that attach to particulate matter, plant material, and other microbes in aquatic environments Appendages increase surface-to-volume ratio of the cells

101 Stalked Bacteria Figure 15.40a

102 Stalked Bacteria Figure 15.40b

103 Stalked Bacteria Figure 15.40c

104 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

105 Growth of Caulobacter Figure 15.41

106 15.16 Budding and Prosthecate/Stalked Bacteria
Gallionella Chemolithotrophic iron-oxidizing bacteria Possess twisted stalk-like structure composed of ferric hydroxide Common in waters draining bogs, iron springs, and other environments rich in Fe2+

107 The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42a

108 The Neutrophilic Ferrous Iron Oxidizer, Gallione Ferruginea
Figure 15.42b

109 V. Delta- and Epsilonproteobacteria
Gliding Myxobacteria Sulfate- and Sulfur-Reducing Proteobacteria The Epsilonproteobacteria

110 15.17 Gliding 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

111 Classification of the Fruiting Myxobacteria

112 Classification of the Fruiting Myxobacteria

113 15.17 Gliding 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

114 15.17 Gliding Myxobacteria Fruiting myxobacteria exhibit complex behavioral patterns and life cycles Vegetative cells are simple, nonflagellated rods that glide across surfaces and obtain their nutrients primarily by lysing other bacteria and utilizing released nutrients Under appropriate conditions, vegetative cells aggregate, construct fruiting bodies, and undergo differentiation into myxospores

115 Myxococcus Figure 15.43a

116 Myxococcus Figure 15.43b

117 Stigmatella aurantiaca
Figure 15.44a

118 Stigmatella aurantiaca
Figure 15.44b

119 Fruiting Bodies of Three Species of Fruiting Myxobacteria
Figure 15.45a

120 Fruiting Bodies of Three Species of Fruiting Myxobacteria
Figure 15.45b

121 Fruiting Bodies of Three Species of Fruiting Myxobacteria
Figure 15.45c

122 15.17 Gliding Myxobacteria The life cycle of fruiting myxobacterium is complex

123 Life Cycle of Myxococcus xanthus
Figure 15.46

124 Swarming in Myxococcus
Figure 15.47a

125 Swarming in Myxococcus
Figure 15.47b

126 Fruiting Body Formation in Chondromyces crocatus
Figure 15.48a

127 Fruiting Body Formation in Chondromyces crocatus
Figure 15.48b

128 Fruiting Body Formation in Chondromyces crocatus
Figure 15.48c

129 Fruiting Body Formation in Chondromyces crocatus
Figure 15.48d

130 Sulfate- and Sulfur-Reducing Proteobacteria
Dissimilative sulfate- and sulfur-reducing bacteria Over 40 genera of Deltaproteobacteria Use SO42- and So 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

131 Sulfate- and Sulfur-Reducing Proteobacteria
Physiology of sulfate-reducing bacteria Group I Oxidize lactate, pyruvate, or ethanol to acetate and excrete fatty acid as an end product Group II Oxidize fatty acids, lactate, succinate, and benzoate to CO2

132 Sulfate- and Sulfur- Reducing Bacteria

133 Enrichment Culture of Sulfate-Reducing Bacteria
Figure 15.49g

134 The Epsilonproteobacteria
Abundant in oxic–anoxic interfaces in sulfur-rich environments e.g., hydrothermal vents Many are autotrophs Using H2, formate, sulfide, or thiosulphate as electron donor Pathogenic and non-pathogenic representatives

135 Characteristics of Key Genera of Epsilonproteobacteria