Hyphomicrobiales | |
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Agrobacterium (SEM image) | |
Scientific classification ![]() | |
Domain: | Bacteria |
Kingdom: | Pseudomonadati |
Phylum: | Pseudomonadota |
Class: | Alphaproteobacteria |
Order: | Hyphomicrobiales Douglas 1957 (Approved Lists 1980) |
Families [1] | |
See text | |
Synonyms [2] | |
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The Hyphomicrobiale' (synonym 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, an important tool 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] [a]
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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.