HOME
The Info List - Proteobacteria



--- Advertisement ---


(i)

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 _ Escherichia
Escherichia
_, _ Salmonella _, _ Vibrio _, _ Helicobacter _, _ Yersinia
Yersinia
_, and many other notable genera . Others are free-living (nonparasitic ), and include many of the bacteria responsible for nitrogen fixation .

Carl Woese
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 after Proteus
Proteus
, a Greek god of the sea capable of assuming many different shapes and is not named after the genus _ Proteus
Proteus
_.

The 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 _ Caulobacter _.

The Betaproteobacteria are highly metabolically diverse and contain chemolithoautotrophs, photoautotrophs , and generalist heterotrophs . The type order is the Burkholderiales
Burkholderiales
, comprising an enormous range of metabolic diversity, including opportunistic pathogens.

The Gammaproteobacteria are the largest class in terms of species with validly published names. The type order is the Pseudomonadales , which include the genera _ Pseudomonas _ and the nitrogen-fixing _ Azotobacter
Azotobacter
_.

The 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 _ Myxococcus _ spp.

The Epsilonproteobacteria
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 _ Campylobacter
Campylobacter
_ spp.

The Oligoflexia are filamentous aerobes. The type order is the Oligoflexales , which contains the genus _Oligoflexus _.

The Acidithiobacillia contain only sulfur-oxidising autotrophs. The type order is the Acidithiobacillales , which includes economically important organisms used in the mining industry such as _ Acidithiobacillus _ spp.

CONTENTS

* 1 Characteristics * 2 Taxonomy * 3 Transformation * 4 References * 5 External links

CHARACTERISTICS

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 photosynthesis .

"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 .

TAXONOMY

The group is defined primarily in terms of ribosomal RNA (rRNA) sequences. The Proteobacteria
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.:

* Alphaproteobacteria : _ Brucella , Rhizobium , Agrobacterium , Caulobacter , Rickettsia
Rickettsia
, Wolbachia _, etc. * Betaproteobacteria : _ Bordetella , Ralstonia , Neisseria , Nitrosomonas _, etc. * Gammaproteobacteria : _ Escherichia
Escherichia
, Shigella
Shigella
, Salmonella , Yersinia
Yersinia
, Buchnera , Haemophilus
Haemophilus
, Vibrio , Pseudomonas _, etc. * Deltaproteobacteria : _ Desulfovibrio , Geobacter , Bdellovibrio _, etc. * Epsilonproteobacteria
Epsilonproteobacteria
: _ Helicobacter , Campylobacter
Campylobacter
, Wolinella _, etc. * Oligoflexia : _Oligoflexus _. * Acidithiobacillia : _ Acidithiobacillus thiooxidans _, __

TRANSFORMATION

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
Proteobacteria
with respect to natural genetic transformation are the medically important human pathogens _ Neisseria gonorrhoeae _ (class beta), _ Haemophilus
Haemophilus
influenzae _ (class gamma) and _ 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 .

REFERENCES

* ^ _A_ _B_ Stackebrandt, E.; Murray, R. G. E.; Truper, H. G. (1988). " Proteobacteria
Proteobacteria
classis nov., a Name for the Phylogenetic Taxon That Includes the "Purple Bacteria
Bacteria
and Their Relatives"". _International Journal of Systematic Bacteriology_. 38 (3): 321–325. doi :10.1099/00207713-38-3-321 . * ^ Garrity, G. M., Bell, J. A. & Lilburn, T. (2005). Phylum
Phylum
XIV. Proteobacteria
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 maint: Extra text: authors list (link ) * ^ Woese, CR (1987). "Bacterial evolution" . _Microbiological reviews_. 51 (2): 221–71. PMC 373105  _. PMID 2439888 . * ^ "Proteobacteria". Discover Life: Tree of Life_. Retrieved 2007-02-09. * ^ 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 Obstetrics and Gynecology_. 213 (4): S131–S137. ISSN 0002-9378 . PMID 26428492 . doi :10.1016/j.ajog.2015.06.039 . * ^ Todar, K. "Pathogenic _E. coli_". _Online Textbook of Bacteriology_. University of Wisconsin–Madison Department of Bacteriology. Retrieved 2007-11-30. * ^ Noel R. Krieg; Don J. Brenner; James T. Staley (2005). _ Bergey's Manual of Systematic Bacteriology: The Proteobacteria_. Springer. ISBN 978-0-387-95040-2 . * ^ Ciccarelli, FD; Doerks, T; Von Mering, C; Creevey, CJ; Snel, B; Bork, P (2006). "Toward automatic reconstruction of a highly resolved tree of life". _Science_. 311 (5765): 1283–7. PMID 16513982 . doi :10.1126/science.1123061 . * ^ Yarza, P; Ludwig, W; Euzéby, J; Amann, R; Schleifer, KH; Glöckner, FO; Rosselló-Móra, R (2010). "Update of the All-Species Living Tree Project based on 16S and 23S rRNA sequence analyses". _Systematic and Applied Microbiology_. 33 (6): 291–9. PMID 20817437 . doi :10.1016/j.syapm.2010.08.001 . . * ^ Williams, KP; Kelly, DP (2013). "Proposal for a new class within the phylum Proteobacteria, Acidithiobacillia classis nov., with the type order Acidithiobacillales, and emended