Enterobacteriaceae is a large family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but one classification places it in the order Enterobacterales of the class Gammaproteobacteria in the phylum Pseudomonadota. In 2016, the description and members of this family were emended based on comparative genomic analyses by Adeolu et al.
Pseudomonadota is a major phylum of Gram-negative bacteria. The renaming of several prokaryote phyla in 2021, including Pseudomonadota, remains controversial among microbiologists, many of whom continue to use the earlier name Proteobacteria, of long standing in the literature. The phylum Proteobacteria includes a wide variety of pathogenic genera, such as Escherichia, Salmonella, Vibrio, Yersinia, Legionella, and many others. Others are free-living (non-parasitic) and include many of the bacteria responsible for nitrogen fixation.
The Rhodospirillales are an order of Pseudomonadota.
Caulobacter crescentus is a Gram-negative, oligotrophic bacterium widely distributed in fresh water lakes and streams. The taxon is more properly known as Caulobacter vibrioides.
The Rhodospirillaceae are a family of Pseudomonadota. The majority are purple nonsulfur bacteria, producing energy through photosynthesis; originally all purple nonsulfur bacteria were included here.
The Nitrosomonadales are an order of the class Betaproteobacteria in the phylum "Pseudomonadota". Like all members of their class, they are Gram-negative.
The Rhizobiaceae is a family of Pseudomonadota comprising multiple subgroups that enhance and hinder plant development. Some bacteria found in the family are used for plant nutrition and collectively make up the rhizobia. Other bacteria such as Agrobacterium tumefaciens and Rhizobium rhizogenes severely alter the development of plants in their ability to induce crown galls or hairy roots, respectively. The family has been of an interest to scientists for centuries in their ability to associate with plants and modify plant development. The Rhizobiaceae are, like all Pseudomonadota, Gram-negative. They are aerobic, and the cells are usually rod-shaped. Many species of the Rhizobiaceae are diazotrophs which are able to fix nitrogen and are symbiotic with plant roots.
Caulobacterales is an order of gram-negative pseudomonadota within the alpha subgroup.
The Burkholderiales are an order of Pseudomonadota. Like all Pseudomonadota, they are Gram-negative. They include several pathogenic bacteria, including species of Burkholderia, Bordetella, and Ralstonia. They also include Oxalobacter and related genera, which are unusual in using oxalic acid as their source of carbon. Other well-studied genera include Alcaligenes, Cupriavidus, Achromobacter, Comamonas, Delftia, Massilia, Duganella, Janthinobacterium, Polynucleobacter, non-pathogenic Paraburkholderia, Caballeronia, Polaromonas, Thiomonas, Collimonas, Hydrogenophaga, Sphaerotilus, Variovorax, Acidovorax, Rubrivivax and Rhodoferax, and Herbaspirillum.
The Legionellales are an order of Pseudomonadota. Like all Pseudomonadota, they are Gram-negative. They comprise two families, typified by Legionella and Coxiella, both of which include notable pathogens. For example, Q fever is caused by Coxiella burnetii and Legionella pneumophila causes Legionnaires' disease and Pontiac fever.
The Rhodocyclaceae are a family of gram-negative bacteria. They are given their own order in the beta subgroup of Pseudomonadota, and include many genera previously assigned to the family Pseudomonadaceae.
The Rhodocyclales are an order of the class Betaproteobacteria in the phylum "Pseudomonadota". Following a major reclassification of the class in 2017, the previously monofamilial order was split into three families:
The Comamonadaceae are a family of the Betaproteobacteria. Like all Pseudomonadota, they are Gram-negative. They are aerobic and most of the species are motile via flagella. The cells are curved rod-shaped.
The Bdellovibrionaceae are a family of Pseudomonadota. They include genera, such as Bdellovibrio and Vampirovibrio, which are unusual parasites that enter other bacteria.
The Methylophilaceae are a family of Pseudomonadota, given their own order. Like all Pseudomonadota, they are Gram-negative. The cells are slightly curved or straight rod-shaped.
The Oxalobacteraceae are a family of bacteria, included in the order Burkholderiales. Like all Pseudomonadota, Oxalobacteraceae are Gram-negative. The family includes strict aerobes, strict anaerobes, and nitrogen-fixing (diazotrophic) members. The cells are curved, vibroid, or straight rod-shaped.
The Piscirickettsiaceae are a family of Pseudomonadota. All species are aerobes found in water. The species Piscirickettsia salmonis is a fish pathogen and causes piscirickettsiosis in salmonid fishes. It lives in cells of infected hosts and cannot be cultured on artificial media. Piscirickettsia salmonis is nonmotile, whereas the other five genera are motile by using a single flagellum.
Betaproteobacteria are a class of Gram-negative bacteria, and one of the eight classes of the phylum Pseudomonadota.
Comamonas is a genus of bacteria in the phylum Pseudomonadota. Like all Pseudomonadota, they are Gram-negative bacteria. Comamonas species are aerobic organisms and motile using bipolar or polar tufts of one to five flagella. Comamonas testosteroni and Comamonas kerstersii have been found to cause infections in people.
Paraburkholderia caribensis is a species of Pseudomonadota. The specific name caribensis refers to the Caribbean Islands, where the bacterium was first found.
