using hydrogen (Hydrogenophaga) or sulfur (Thiomonas)
as electron donors. Family Oxalobacteraceae (Oxalobacter)
is part of this order. The order Hydrogenophilales with a
single family (Hydrogenophilaceae) corresponds to aerobic
chemolithotrophic bacteria using hydrogen (Hydrogenophilus) or sulfur (Thiobacillus) as electron donors.
The order Methylophilales concerns methylotrophic bacteria
(cf. Sect. 3.4.2) grouped in a family (Methylophilaceae) with
genera Methylophilus, Methylobacillus, etc. The order
Neisseriales with a family (Neisseriaceae) contains very pathogenic Gram-negative cocci (Neisseria gonorrhoeae, Neisseria
pneumoniae, Neisseria meningitidis) but also bacteria isolated
from soil or water (Aquaspirillum, Chromobacterium).
The order Nitrosomonadales concerns chemolithotrophic
bacteria with ammonium oxidizing family Nitrosomonadaceae (Nitrosospira, Nitrosomonas), ferro-oxidant family Gallionellaceae (Gallionella), and family Spirillaceae
with chemoorganotrophic bacteria (Spirillum). Many filamentous bacteria are also present in this class with filamentous bacteria in sewage sludge (Sphaerotilus, Zooglea) or
iron-oxidizing bacteria (Leptothrix).
The Class Gammaproteobacteria
It includes the largest number of Proteobacteria grouped
in 13 orders. One (the Chromatiales) contains all the
phototrophic purple sulfur bacteria oxidizing sulfide during
anoxygenic photosynthesis. These bacteria accumulate intracellular sulfur globules (family Chromatiaceae with
Chromatium as the type genus (Fig. 6.14c, e, f) and related
genera, and Thiocapsa, Halothiocapsa (Fig. 6.14b),
Lamprobacter, Thiodictyon (Fig. 6.14q) Thiococcus,
Thiocystis, and Thiopedia) or extracellular (Ectothiorhodospiraceae family with the halophilic genus Ectothiorhodospira
(Fig. 6.14k) or extreme halophilic Halorhodospira) and nonphotosynthetic bacteria (Nitrococcus).
The Xanthomonadales with a family (Xanthomonadaceae)
contain chemoorganotrophic aerobic bacteria often isolated
from soil and plant pathogens (Xanthomonas, Xylella, etc.).
The Pseudomonadales include two families, Pseudomonadaceae with the genera Pseudomonas, common bacteria of
soil and water, some plant pathogens, or nosocomial diseasecausing (Pseudomonas aeruginosa), Azomonas, Rhizobacter,
and Moraxellaceae with Moraxella, Acinetobacter, which are
encountered in soils.
In the class Gammaproteobacteria, there is in particular
the order Enterobacteriales for all Enterobacteriaceae, bacteria capable of chemoorganotrophic aerobic or anaerobic respiration (respiring nitrate) and fermentation (cf. Sect. 3.3.3),
with coliforms (Klebsiella, Hafnia, Citrobacter, Enterobacter)
and Escherichia coli, commensal or pathogenic bacteria being
the microorganism most studied in terms of physiology and
genetics, Salmonella, agents of typhoid and paratyphoid fever
(Salmonella typhi, Salmonella paratyphi), Proteus, and Shigella (Shigella sonnei). In this order are also present Yersinia
pestis, the agent of plague, and symbionts of insects or
nematodes as Photorhabdus.
The order Vibrionales with a family Vibrionaceae,
contains chemoorganotrophic bacteria isolated from waters,
particularly coastal waters or estuaries as the genus Vibrio
with Vibrio cholerae (cholera agent) and many marine Vibrio causing infections or poisoning of animal (fish) or
human, and the genera Salinivibrio or Photobacterium, the
latter containing luminescent bacteria with an enzyme, luciferase, also present in prokaryote light organs of certain deep
marine organisms.
The Aeromonadales as Vibrionales and Enterobacteriales
are also aerobic bacteria, facultative anaerobes (capable of
respiring and fermentation) or strict anaerobes include two
families: Aeromonadaceae with the genus Aeromonas, freshwater bacteria, some of which are pathogenic of fish
(Aeromonas salmonicida), and Succinivibrionaceae which
contain genera represented by strict fermentative bacteria
(Succinivibrio, Ruminobacter, Anaerobiospirillum) isolated
from fermenters or rumen.
The order Pasteurellales with a family (Pasteurellaceae)
includes the genus Pasteurella chemoheterotrophic bacteria
responsible for pulmonary infections in animals and
Haemophilus influenzae pathogen of respiratory track, the
first bacterium completely sequenced in 1995 (Fleischmann
et al. 1995).
The order Legionellales with a single family
(Legionellaceae) contains a single genus (Legionella)
corresponding to Legionella pneumophila, the agent of
Legionnaires’ disease, surprise guest at the American
Legionnaires Convention Philadelphia 1976, often isolated
from ventilation systems, water circulation or refrigeration
industries and communities, and responsible for serious lung
infections.
The order Oceanospirillales includes aerobic chemoorganotrophic marine bacteria also capable of respiring nitrate,
grouped into two families, Oceanospirillaceae with genera
Oceanospirillum, Marinospirillum, and Halomonadaceae
with genera Halomonas or Alcanivorax, bacteria capable of
totally degrading hydrocarbons.
The Alteromonadales with the family Alteromonadaceae
also comprise chemoorganotrophs marine halophilic or
halotolerant bacteria (Alteromonas, Marinobacter, Marinobacterium) or bacteria living at very cold temperatures
(Psychromonas).
The order Thiotricales is represented by chemolithotrophic
sulfur-oxidizing bacteria filamentous and often gliding
(Thiothrix, Thiomargarita, Thiobacterium, Thioploca,
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as electron donors. Family Oxalobacteraceae (Oxalobacter)
is part of this order. The order Hydrogenophilales with a
single family (Hydrogenophilaceae) corresponds to aerobic
chemolithotrophic bacteria using hydrogen (Hydrogenophilus) or sulfur (Thiobacillus) as electron donors.
The order Methylophilales concerns methylotrophic bacteria
(cf. Sect. 3.4.2) grouped in a family (Methylophilaceae) with
genera Methylophilus, Methylobacillus, etc. The order
Neisseriales with a family (Neisseriaceae) contains very pathogenic Gram-negative cocci (Neisseria gonorrhoeae, Neisseria
pneumoniae, Neisseria meningitidis) but also bacteria isolated
from soil or water (Aquaspirillum, Chromobacterium).
The order Nitrosomonadales concerns chemolithotrophic
bacteria with ammonium oxidizing family Nitrosomonadaceae (Nitrosospira, Nitrosomonas), ferro-oxidant family Gallionellaceae (Gallionella), and family Spirillaceae
with chemoorganotrophic bacteria (Spirillum). Many filamentous bacteria are also present in this class with filamentous bacteria in sewage sludge (Sphaerotilus, Zooglea) or
iron-oxidizing bacteria (Leptothrix).
The Class Gammaproteobacteria
It includes the largest number of Proteobacteria grouped
in 13 orders. One (the Chromatiales) contains all the
phototrophic purple sulfur bacteria oxidizing sulfide during
anoxygenic photosynthesis. These bacteria accumulate intracellular sulfur globules (family Chromatiaceae with
Chromatium as the type genus (Fig. 6.14c, e, f) and related
genera, and Thiocapsa, Halothiocapsa (Fig. 6.14b),
Lamprobacter, Thiodictyon (Fig. 6.14q) Thiococcus,
Thiocystis, and Thiopedia) or extracellular (Ectothiorhodospiraceae family with the halophilic genus Ectothiorhodospira
(Fig. 6.14k) or extreme halophilic Halorhodospira) and nonphotosynthetic bacteria (Nitrococcus).
The Xanthomonadales with a family (Xanthomonadaceae)
contain chemoorganotrophic aerobic bacteria often isolated
from soil and plant pathogens (Xanthomonas, Xylella, etc.).
The Pseudomonadales include two families, Pseudomonadaceae with the genera Pseudomonas, common bacteria of
soil and water, some plant pathogens, or nosocomial diseasecausing (Pseudomonas aeruginosa), Azomonas, Rhizobacter,
and Moraxellaceae with Moraxella, Acinetobacter, which are
encountered in soils.
In the class Gammaproteobacteria, there is in particular
the order Enterobacteriales for all Enterobacteriaceae, bacteria capable of chemoorganotrophic aerobic or anaerobic respiration (respiring nitrate) and fermentation (cf. Sect. 3.3.3),
with coliforms (Klebsiella, Hafnia, Citrobacter, Enterobacter)
and Escherichia coli, commensal or pathogenic bacteria being
the microorganism most studied in terms of physiology and
genetics, Salmonella, agents of typhoid and paratyphoid fever
(Salmonella typhi, Salmonella paratyphi), Proteus, and Shigella (Shigella sonnei). In this order are also present Yersinia
pestis, the agent of plague, and symbionts of insects or
nematodes as Photorhabdus.
The order Vibrionales with a family Vibrionaceae,
contains chemoorganotrophic bacteria isolated from waters,
particularly coastal waters or estuaries as the genus Vibrio
with Vibrio cholerae (cholera agent) and many marine Vibrio causing infections or poisoning of animal (fish) or
human, and the genera Salinivibrio or Photobacterium, the
latter containing luminescent bacteria with an enzyme, luciferase, also present in prokaryote light organs of certain deep
marine organisms.
The Aeromonadales as Vibrionales and Enterobacteriales
are also aerobic bacteria, facultative anaerobes (capable of
respiring and fermentation) or strict anaerobes include two
families: Aeromonadaceae with the genus Aeromonas, freshwater bacteria, some of which are pathogenic of fish
(Aeromonas salmonicida), and Succinivibrionaceae which
contain genera represented by strict fermentative bacteria
(Succinivibrio, Ruminobacter, Anaerobiospirillum) isolated
from fermenters or rumen.
The order Pasteurellales with a family (Pasteurellaceae)
includes the genus Pasteurella chemoheterotrophic bacteria
responsible for pulmonary infections in animals and
Haemophilus influenzae pathogen of respiratory track, the
first bacterium completely sequenced in 1995 (Fleischmann
et al. 1995).
The order Legionellales with a single family
(Legionellaceae) contains a single genus (Legionella)
corresponding to Legionella pneumophila, the agent of
Legionnaires’ disease, surprise guest at the American
Legionnaires Convention Philadelphia 1976, often isolated
from ventilation systems, water circulation or refrigeration
industries and communities, and responsible for serious lung
infections.
The order Oceanospirillales includes aerobic chemoorganotrophic marine bacteria also capable of respiring nitrate,
grouped into two families, Oceanospirillaceae with genera
Oceanospirillum, Marinospirillum, and Halomonadaceae
with genera Halomonas or Alcanivorax, bacteria capable of
totally degrading hydrocarbons.
The Alteromonadales with the family Alteromonadaceae
also comprise chemoorganotrophs marine halophilic or
halotolerant bacteria (Alteromonas, Marinobacter, Marinobacterium) or bacteria living at very cold temperatures
(Psychromonas).
The order Thiotricales is represented by chemolithotrophic
sulfur-oxidizing bacteria filamentous and often gliding
(Thiothrix, Thiomargarita, Thiobacterium, Thioploca,
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P. Caumette et al.