Proteobacteria

The Proteobacteria represent one of the larger groups of the domain of bacteria considered as divisions or as strains (in the sense of phylum). They include many important nitrogen-fixing bacteria and pathogens.

The name Proteobacteria is derived from the Greek god Proteus, who could change shape, and refers to the diversity of forms in this group. It is therefore not defined morphologically, but very much by related RNA sequences. The cell walls of Proteobacteria are notably composed of single- to few-layered murein and lipopolysaccharides, hence they are Gram-negative. However, some species are also Gram-variant reactive, such as Azospirillum brasilense and species of Methylobacterium. Many species possess flagella, others are able to glide.

Some subgroups such as the Rhodospirillaceae (purple bacteria) and Chromatiaceae (sulfur purple bacteria) are capable of anoxygenic photosynthesis under anoxic conditions. For this purpose, they use organic substances, hydrogen sulphide, sulphur or hydrogen as electron donors and therefore do not produce elemental oxygen.

The subgroup Myxobacteria is the only known group of proteobacteria in the transitional field between unicellular and multicellular life. Myxobacteria form multicellular fruiting bodies with spores, a convergence to slime moulds.

The Proteobacteria were initially divided into five main groups, considered as a class, and given the Greek letters Alpha to Epsilon as prefixes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, and Epsilonproteobacteria. Over time, four additional classes have been described (as of 2020), the "Zetaproteobacteria", Acidithiobacillia, Hydrogenophilalia and Oligoflexia.

The mitochondria of eukaryotes, all living organisms with a cell nucleus, possibly originate from endosymbiontic proteobacteria (See: Endosymbiont hypothesis).

Systematics

The following are some important orders, families, and genera of the eight classes of Proteobacteria. The article Systematics of bacteria is considered a reference in Wikipedia and contains a larger selection of taxa in the phylum Proteobacteria.

Acidithiobacillia

·         Order I. Acidithiobacillales

·         Acidithiobacillaceae family

·         genus Acidithiobacillus

·         Thermithiobacillaceae family

·         genus Thermithiobacillus

Alphaproteobacteria

·         Order I. Rhodospirillales

·         Family I. Rhodospirillaceae (non-sulfur-processing purple bacteria)

·         Family II Acetobacteraceae; triv. acetic acid bacteria (vinegar)

·         Order II Rickettsiales

·         Order VI Rhizobiales

·         Family I. Rhizobiaceae

·         Genus I. Rhizobium

·         Family II. Bartonellaceae

·         Family III Brucellaceae

and other taxa

Betaproteobacteria

·         Order I. Burkholderial

·         Order IV Neisseriales

·         Family I. Neisseriaceae

·         Genus I. Neisseria

·         Genus IX Kingella

and other taxa

Gammaproteobacteria

·         Order I. Chromatiales

·         Family I. Chromatiaceae (triv. sulfur purple bacteria)

·         Family II. Ectothiorhodospiraceae

·         Order II "Xanthomonadales".

·         Family I. "Xanthomonadaceae"

·         Genus I. Xanthomonas

·         Genus VII Stenotrophomonas

Within the LPSN (List of Prokaryotic names with Standing in Nomenclature), an important listing of the systematics of bacteria, the order Xanthomonadales is no longer listed. This order and the single family Xanthomonadaceae that was added were dissolved due to recent research. Many of the genera are now placed in the order Lysobacterales, others are not yet assigned to any specific order. However, the old system is still in use and is, for example, still used in the taxonomy database of the NCBI (National Center for Biotechnology Information), an important source of information on bacteria.

·         Order IV Thiotrichales

·         Family I. Thiotrichaceae

·         Genus VII Thiomargarita

·         Order VIII Pseudomonales

·         Family I. Pseudomonaceae

·         Genus I. Pseudomonas

·         Family II. Moraxellaceae

·         Genus I. Moraxella

·         Genus II Acinetobacter

·         Order X. "Vibrionales"

·         Family I. Vibrionaceae

·         Genus I. Vibrio

·         Order XII. Enterobacterales, previously referred to as order "Enterobacteriales

·         Budviciaceae family

·         Enterobacteriaceae family

·         Erwiniaceae family

·         Hafniaceae family

·         Morganellaceae family

·         Pectobacteriaceae family

·         Thorselliaceae family

·         Yersiniaceae family

·         Order XIII Pasteurellales

·         Family I. Pasteurellaceae

·         Genus I. Pasteurella

·         Genus III. Haemophilus

·         Order XIV Oceanospirillales

·         Family I. Alcanivoracaceae

·         Family II. Hahellaceae

·         Family III. Halomonadaceae

·         Genus I Halomonas

·         Family IV. Litoricolaceae

·         Family V. Oceanospirillacae

·         Family VI. Oleiphilaceae

·         Family VII "Saccharospirillaceae"

and other taxa

Hydrogenophilalia

·         Order I. Hydrogenophilic

·         Family Hydrogenophilaceae

with only one genus, Hydrogenophilus

Deltaproteobacteria

·         Order I. Desulfovibrionales

·         Family I. Desulfovibrionaceae

·         genus Desulfovibrio

·         Order II Myxococcales (Myxobacteria)

·         Myxococcaceae family

·         Order Bdellovibrionales

·         Family Bdellovibrionaceae

·         genus Bdellovibrio

and other taxa

Epsilonproteobacteria

·         Order Campylobacterales

·         Campylobacteraceae family

·         genus Campylobacter

·         Helicobacteraceae family

·         helicobacter genus

·         Order Nautiliales

·         Family Nautiliaceae

·         nautile genus

and other taxa

Oligoflexia

·         Order I. Oligoflexal

·         Oligoflexaceae family

·         Oligoflexus genus

·         Order II Silvanigrellales

·         Silvanigrellalaceae

·         genus Silvanigrella

"Zetaproteobacteria"

·         family "Mariprofundaceae", with the only genus Mariprofundus