The "PROTEOBACTERIA" are a major phylum of
Gram-negative bacteria .
The name of the phylum has never been validly published as no type
genus has been proposed, thus it must be styled in quotation marks as
the name has no standing in nomenclature. They include a wide variety
of pathogens , such as
Yersinia , and many other notable genera . Others are
free-living (nonparasitic ), and include many of the bacteria
responsible for nitrogen fixation .
Carl Woese established this grouping in 1987, calling it informally
the "purple bacteria and their relatives". Because of the great
diversity of forms found in this group, the "Proteobacteria" are named
Proteus , a Greek god of the sea capable of assuming many
different shapes and is not named after the genus
Alphaproteobacteria grow at very low levels of nutrients and have
unusual morphology such as stalks and buds. They include
agriculturally important bacteria capable of inducing nitrogen
fixation in symbiosis with plants. The type order is the
Caulobacterales , comprising stalk-forming bacteria such as
Betaproteobacteria are highly metabolically diverse and contain
chemolithoautotrophs, photoautotrophs , and generalist heterotrophs .
The type order is the
Burkholderiales , comprising an enormous range
of metabolic diversity, including opportunistic pathogens.
Gammaproteobacteria are the largest class in terms of species
with validly published names. The type order is the
which include the genera
Pseudomonas and the nitrogen-fixing
Deltaproteobacteria include bacteria that are predators on other
bacteria and are important contributors to the anerobic side of the
sulfur cycle. The type order is the
Myxococcales , which includes
organisms with self-organising abilities such as
Epsilonproteobacteria are often slender, Gram-negative rods that
are helical or curved. The type order is the
Campylobacterales , which
includes important food pathogens such as
The Oligoflexia are filamentous aerobes. The type order is the
Oligoflexales , which contains the genus Oligoflexus .
Acidithiobacillia contain only sulfur-oxidising autotrophs. The
type order is the
Acidithiobacillales , which includes economically
important organisms used in the mining industry such as
* 1 Characteristics
* 2 Taxonomy
* 3 Transformation
* 4 References
* 5 External links
All "Proteobacteria" are Gram-negative, though some may stain
Gram-positive or Gram-variable in practice, with an outer membrane
mainly composed of lipopolysaccharides . Many move about using
flagella , but some are nonmotile or rely on bacterial gliding . The
last include the Myxobacteriales , an order of bacteria that can
aggregate to form multicellular fruiting bodies. Also, a wide variety
in the types of metabolism exists. Most members are facultatively or
obligately anaerobic ,
Chemolithoautotrophic , and heterotrophic , but
numerous exceptions occur. A variety of genera, which are not closely
related to each other, convert energy from light through
"Proteobacteria" are associated with the imbalance of microbiota of
the lower reproductive tract of women. These species are associated
with inflammation. Protobacteria are part of normal, healthy
placental microbiome .
The group is defined primarily in terms of ribosomal RNA (rRNA)
Proteobacteria are divided into six classes with
validly published names, referred to by the
Greek letters alpha
through epsilon and the
Acidithiobacillia and Oligoflexia. These were
previously regarded as subclasses of the phylum, but they are now
treated as classes . These classes are monophyletic . The genus
Acidithiobacillus , part of the
Gammaproteobacteria until it was
transferred to class
Acidithiobacillia in 2013, is paraphyletic to
Betaproteobacteria according to multigenome alignment studies .
Proteobacterial classes with validly published names include some
prominent genera: e.g.:
Wolbachia , etc.
Nitrosomonas , etc.
Yersinia , Buchnera ,
Pseudomonas , etc.
* Oligoflexia : Oligoflexus .
Acidithiobacillus thiooxidans ,
Transformation , a process in which genetic material passes from
bacterium to another, has been reported in at least 30 species of
Proteobacteria distributed in the classes alpha, beta, gamma and
epsilon. The best-studied
Proteobacteria with respect to natural
genetic transformation are the medically important human pathogens
Neisseria gonorrhoeae (class beta),
Haemophilus influenzae (class
Helicobacter pylori (class epsilon). Natural genetic
transformation is a sexual process involving DNA transfer from one
bacterial cell to another through the intervening medium and the
integration of the donor sequence into the recipient genome. In
pathogenic Proteobacteria, transformation appears to serve as a DNA
repair process that protects the pathogen’s DNA from attack by their
host’s phagocytic defenses that employ oxidative free radicals .
* ^ A B Stackebrandt, E.; Murray, R. G. E.; Truper, H. G. (1988).
Proteobacteria classis nov., a Name for the Phylogenetic Taxon That
Includes the "Purple
Bacteria and Their Relatives"". International
Journal of Systematic Bacteriology. 38 (3): 321–325. doi
* ^ Garrity, G. M., Bell, J. A. & Lilburn, T. (2005).
Proteobacteria phyl. nov. In: Bergey’s Manual of Systematic
Bacteriology, 2nd edn, vol. 2 (The Proteobacteria), part B (The
Gammaproteobacteria), p. 1. Edited by D. J. Brenner, N. R. Krieg, J.
T. Staley & G. M. Garrity. New York: Springer.
* ^ Madigan, M. and J. Martinko. (eds.) (2005). Brock Biology of
Microorganisms (11th ed.). Prentice Hall. ISBN 0-13-144329-1 . CS1
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* ^ Woese, CR (1987). "Bacterial evolution" . Microbiological
reviews. 51 (2): 221–71. PMC 373105 . PMID 2439888 .
* ^ "Proteobacteria". Discover Life: Tree of Life. Retrieved
* ^ Bennett, John (2015). Mandell, Douglas, and Bennett's
principles and practice of infectious diseases. Philadelphia, PA:
Elsevier/Saunders. ISBN 9781455748013 ; Access provided by the
University of Pittsburgh
* ^ Mor, Gil; Kwon, Ja-Young (2015). "Trophoblast-microbiome
interaction: a new paradigm on immune regulation". American Journal of
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26428492 . doi :10.1016/j.ajog.2015.06.039 .
* ^ Todar, K. "Pathogenic E. coli". Online Textbook of
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* ^ Noel R. Krieg; Don J. Brenner; James T. Staley (2005). Bergey's
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* ^ Williams, KP; Kelly, DP (2013). "Proposal for a new class
within the phylum Proteobacteria,
Acidithiobacillia classis nov., with
the type order Acidithiobacillales, and emended description of the
class Gammaproteobacteria". International Journal of Systematic and
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* ^ Interactive Tree of Life
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