Hyphomicrobiales | |
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Agrobacterium (SEM image) | |
Scientific classification | |
Domain: | Bacteria |
Phylum: | Pseudomonadota |
Class: | Alphaproteobacteria |
Order: | Hyphomicrobiales Douglas 1957 (Approved Lists 1980) |
Families [1] | |
See text | |
Synonyms [2] | |
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The Hyphomicrobiales (synonom Rhizobiales) are an order of Gram-negative Alphaproteobacteria.
The rhizobia, which fix nitrogen and are symbiotic with plant roots, appear in several different families. The four families Nitrobacteraceae , Hyphomicrobiaceae , Phyllobacteriaceae , and Rhizobiaceae contain at least several genera of nitrogen-fixing, legume-nodulating, microsymbiotic bacteria. Examples are the genera Bradyrhizobium and Rhizobium . Species of the Methylocystaceae are methanotrophs; they use methanol (CH3OH) or methane (CH4) as their sole energy and carbon sources. Other important genera are the human pathogens Bartonella and Brucella , as well as Agrobacterium (useful in genetic engineering).
The following genus has not been assigned to a family:
These taxa have been published, but have not been validated according to the Bacteriological Code:
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature [7] and the phylogeny is based on whole-genome sequences. [2] [lower-alpha 1]
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Natural genetic transformation has been reported in at least four Hyphomicrobiales species: Agrobacterium tumefaciens , [8] Methylobacterium organophilum , [9] Ensifer adhaerens , [10] and Bradyrhizobium japonicum . [11] 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 by homologous recombination.
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.
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.
Caulobacteraceae is a family of Pseudomonadota within the alpha subgroup. Like all Pseudomonadota, the Caulobacteraceae are gram-negative. Caulobacteraceae includes the genera Asticcacaulis, Brevundimonas, Phenylobacterium and Caulobacter.
Caulobacterales is an order of gram-negative pseudomonadota within the alpha subgroup.
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 Brucellaceae are a family of the Gram-negative Hyphomicrobiales. They are named after Sir David Bruce, a Scottish microbiologist. They are aerobic chemoorganotrophes. The family comprises pathogen and soil bacteria
The Holosporaceae are a family of bacteria. The member Holospora is an intracellular parasite found in the unicellular protozoa Paramecium.
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.
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.
Zavarzinia compransoris is a Gram-negative soil bacterium that comprises the only current member of the genus Zavarzinia. It is named after the Russian microbiologist Georgi Alexandrovich Zavarzin. Zavarzinia is motile by using a polar flagellum. The cells are curved rod-shaped.
Aminobacter aminovorans is a Gram-negative soil bacteria.
Afipia carboxidovorans is a Gram-negative soil bacterium. It is aerobic, the cells are rod-shaped.
Devosia is a genus of Gram-negative soil bacteria. It is named after the Belgian microbiologist Paul De Vos. They are motile by flagella, the cells are rod-shaped.
Methylobacillus is a genus of Gram-negative methylotrophic bacteria. The cells are rod-shaped.
Burkholderia vietnamiensis is a species of bacteria. It can be found as an opportunistic pathogen in patients with cystic fibrosis or other immunocompromising illnesses. It differs from most Burkholderia species in that it is often susceptible to aminoglycosides, but not polymyxin B. Many isolates have been found to be catalase positive. B. vietnamiensis is able to fix N
2.
Ensifer is a genus of nitrogen-fixing bacteria (rhizobia), three of which have been sequenced.
In taxonomy, Ahrensia is a genus of the Hyphomicrobiales. Ahrensia is named after the German microbiologist R. Ahrens. The cells are rod-shaped and motile. They are strictly aerobic.
The Sphingomonadales are an order of the Alphaproteobacteria.
The Marinilabiliaceae are a family of bacteria.