Proteobacteria is a major phylum of Gram-negative bacteria. They include a wide variety of pathogenic genera, such as Escherichia, Salmonella, Vibrio, Helicobacter, Yersinia, Legionellales, and many others.[10] 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".[11] Because of the great diversity of forms found in this group, it was named after Proteus, a Greek god of the sea capable of assuming many different shapes and is not named after the Proteobacteria genus Proteus.[1][12]
| Proteobacteria | |
|---|---|
 | |
| Escherichia coli | |
Scientific classification | |
| Domain: | Bacteria |
| Phylum: | Proteobacteria Stackebrandt et al., 1988,[1]Garrity et al. 2005[2] |
| Classes | |
Alphaproteobacteria[3] | |
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 latter include the myxobacteria, 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 and anoxygenic photosynthesis.
"Proteobacteria" are associated with the imbalance of microbiota of the lower reproductive tract of women. These species are associated with inflammation.[13]
Some Alphaproteobacteria can grow at very low levels of nutrients and have unusual morphology such as stalks and buds. Others 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 mitochondria of eukaryotes are thought to be descendants of an alphaproteobacterium.[14]
The 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.
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.
The Deltaproteobacteria include bacteria that are predators on other bacteria and are important contributors to the anaerobic side of the sulfur cycle. The type order is the Myxococcales, which includes organisms with self-organising abilities such as Myxococcus spp.
The 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 spp.
The Zetaproteobacteria are iron-oxidizing neutrophilic chemolithoautotrophs, distributed worldwide in estuaries and marine habitats. The type order is the Mariprofundales.
The Hydrogenophilalia are obligate thermophiles and include heterotrophs and autotrophs. The type order is the Hydrogenophilales.
The Acidithiobacillia contain only sulfur, iron, and uranium-oxidising autotrophs. The type order is the Acidithiobacillales, which includes economically important organisms used in the mining industry such as Acidithiobacillus spp.
The Oligoflexia are filamentous aerobes. The type order is the Oligoflexales, which contains the genus Oligoflexus.
Proteobacterial classes with validly published names include some prominent genera:[21] e.g.:
- Alphaproteobacteria: Brucella, Rhizobium, Agrobacterium, Caulobacter, Rickettsia, Wolbachia, etc.
- Betaproteobacteria: Bordetella, Ralstonia, Neisseria, Nitrosomonas, etc.
- Gammaproteobacteria: Escherichia, Shigella, Salmonella, Yersinia, Buchnera, Haemophilus, Vibrio, Pseudomonas, etc.
- Deltaproteobacteria: Desulfovibrio, Geobacter, Bdellovibrio, etc.
- Epsilonproteobacteria: Helicobacter, Campylobacter, Wolinella, etc.
- Zetaproteobacteria: Mariprofundus, Ghiorsea
- Oligoflexia: Oligoflexus.
- Acidithiobacillia: Acidithiobacillus thiooxidans, Thermithiobacillus tepidarius
- Hydrogenophilalia: Hydrogenophilus thermoluteolus, Tepidiphilus margaritifer
https://en.wikipedia.org/wiki/Proteobacteria
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