Update in progress: Jan 2016
This page lists all of the current validly-published binomial names for the rhizobia, which currently consists of 98 species in 13 genera.
Rhizobia are nitrogen-fixing bacteria that form root nodules on legume plants. Most of these bacterial species are in the Rhizobiacae family in the alpha-proteobacteria and are in either the Rhizobium, Mesorhizobium, Ensifer, or Bradyrhizobium genera. However recent research has shown that there are many other rhizobial species in addition to these. In some cases these new species have arisen through lateral gene transfer of symbiotic genes. The list below is not 'official' by any means, and it is merely my compilation and interpretation of the literature. An alternative list is maintained by the "ICSP Subcommittee on the taxonomy of Rhizobium and Agrobacterium".
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It is important to note that there are other non-rhizobial species present in these genera. For example in the Rhizobium genus, there is Rhizobium radiobacter — formerly known as Agrobacterium tumefaciens. However these species are not listed here, as the 'Agrobacteria' do not form nitrogen fixing symbiotic root nodules (unless they contain a symbiotic plasmid — see Velazquez et al., 2005). I have another page about these bacteria that could be confused with 'true' rhizobia. To see all of the currently valid members of a genus, including non-rhizobial species, click on the name of the genus in the text in each section. This will take you to the LPSN taxonomy website.
This page was compiled from my own research; a paper by J.G. Howieson and J. Brockwell presented at the 14th Australian Nitrogen Fixation Conference, and the NCBI and LPSN websites. This page is updated regularly. If you know of any additions or corrections please email me. I do try to keep up, but finding new rhizobial genera in particular is difficult. To compare the differences between updates check the change log. This page can be cited as:
Weir, B.S. (2016) The current taxonomy of rhizobia. NZ Rhizobia website. https://www.rhizobia.co.nz/taxonomy/rhizobia Last updated: X Jan, 2016
Rhizobium
class: Alphaproteobacteria order: Rhizobiales family: Rhizobiaceae
The genus Rhizobium (Frank 1889) was the first named (from Latin meaning 'root living'), and for many years this was a 'catch all' genus for all rhizobia. Some species were later moved in to new genera based on phylogenetic analyses. It currently consists of 49 rhizobial species (and 11 non rhizobial species). Rhizobium in New Zealand.
| Rhizobium alamii | Berge et al. (2009) |
| Rhizobium alkalisoli | Lu et al. (2009b), See note B |
| Rhizobium azibense | |
| Rhizobium calliandrae | |
| Rhizobium cauense | |
| Rhizobium cellulosilyticum | GarcĂa-Fraile et al. (2007) |
| Rhizobium daejeonense | |
| Rhizobium endophyticum | LĂłpez-LĂłpez et al. (2011) |
| Rhizobium etli | |
| Rhizobium fabae | |
| Rhizobium freirei | |
| Rhizobium galegae | See note B |
| Rhizobium gallicum | |
| Rhizobium giardinii | |
| Rhizobium grahamii | |
| Rhizobium hainanense | |
| Rhizobium halophytocola | |
| Rhizobium herbae | Ren et al. (2011b) |
| Rhizobium huautlense | See note B |
| Rhizobium indigoferae | |
| Rhizobium jaguaris | |
| Rhizobium laguerreae | |
| Rhizobium leguminosarum | Type species. See note A |
| Rhizobium leucaenae | formerly Rhizobium tropici type A strains |
| Rhizobium loessense | formerly Rhizobium huanglingense |
| Rhizobium lusitanum | |
| Rhizobium mayense | |
| Rhizobium mesoamericanum | |
| Rhizobium mesosinicum | Lin et al. (2009) |
| Rhizobium miluonense | Gu et al. (2008) |
| Rhizobium mongolense | |
| Rhizobium multihospitium | Han et al. (2008) |
| Rhizobium oryzae | Peng et al. (2008) |
| Rhizobium paranaense | |
| Rhizobium petrolearium | |
| Rhizobium phaseoli | Confirmed as a species. Ramirez-Bahena et al. (2008) |
| Rhizobium pisi | Ramirez-Bahena et al. (2008) |
| Rhizobium tibeticum | Hou et al. (2009) |
| Rhizobium sophorae | |
| Rhizobium sophoriradicis | |
| Rhizobium sphaerophysae | |
| Rhizobium sullae | formerly Rhizobium hedysari |
| Rhizobium taibaishanense | |
| Rhizobium tropici | |
| Rhizobium tubonense | Zhang et al. (2011) |
| Rhizobium undicola | formerly Allorhizobium undicola |
| Rhizobium vallis | |
| Rhizobium vignae | Ren et al. (2011) |
| Rhizobium yanglingense |
A — Rhizobium trifolii is a later synonym of R. leguminosarum. R. phaseoli is a valid separate species, and some isolates formerly known as R. leguminosarum are now R. pisi (Ramirez-Bahena et al. 2008).
B — The genus Neorhizobium was created by Mousavi et al. 2013 including R. alkalisoli, R. galegae, and R. huautlense. I choose not to follow this taxonomy as I feel it is incomplete, and not useful without a wider analysis.
NB: for non rhizobia Rhizobium such as R. soli and R. radiobacter see the not rhizobia page.
Mesorhizobium
class: Alphaproteobacteria order: Rhizobiales family: Phyllobacteriaceae
The genus Mesorhizobium was described by Jarvis et al. in 1997. Several Rhizobium species were transferred to this genus. It currently consists of 21 rhizobia species (and 1 non-rhizobial species). Mesorhizobium in New Zealand.
| Mesorhizobium abyssinicae | |
| Mesorhizobium albiziae | Wang et al. (2007) |
| Mesorhizobium alhagi | Chen et al. (2010) |
| Mesorhizobium amorphae | |
| Mesorhizobium australicum | Nandasena et al. (2009) |
| Mesorhizobium camelthorni | Chen et al. (2011) |
| Mesorhizobium caraganae | Wang et al. (2007) |
| Mesorhizobium chacoense | |
| Mesorhizobium ciceri | formerly Rhizobium ciceri |
| Mesorhizobium erdmanii | |
| Mesorhizobium gobiense | Han et al. (2008b) |
| Mesorhizobium hawassense | |
| Mesorhizobium huakuii | formerly Rhizobium huakuii |
| Mesorhizobium jarvisii | |
| Mesorhizobium loti | formerly Rhizobium loti, Type species |
| Mesorhizobium mediterraneum | formerly Rhizobium mediterraneum |
| Mesorhizobium metallidurans | Vidal et al. (2009) |
| Mesorhizobium muleiense | |
| Mesorhizobium opportunistum | Nandasena et al. (2009) |
| Mesorhizobium plurifarium | |
| Mesorhizobium qingshengii | |
| Mesorhizobium robiniae | Zhou et al. (2010) |
| Mesorhizobium sangaii | |
| Mesorhizobium shangrilense | Lu et al. (2009) |
| Mesorhizobium shonense | |
| Mesorhizobium silamurunense | |
| Mesorhizobium septentrionale | |
| Mesorhizobium tamadayense | |
| Mesorhizobium tarimense | Han et al. (2008b) |
| Mesorhizobium temperatum | |
| Mesorhizobium tianshanense | formerly Rhizobium tianshanense |
Ensifer (formerly Sinorhizobium)
class: Alphaproteobacteria order: Rhizobiales family: Rhizobiaceae
The Sinorhizobium genus was described by Chen et al. in 1988. However some recent studies show that Sinorhizobium and the genus Ensifer (Casida, 1982) belong to a single taxon. Ensifer is the earlier heterotypic synonym (it was named first) and thus takes priority (Young, 2003). This means that all Sinorhizobium spp. must be renamed as Ensifer spp. according to the Bacteriological code. There has been some discussion in the literature if Ensifer or Sinorhizobium is correct Young (2010), this website follows the opinion of the Judicial Commission, and will use Ensifer. The genus currently consists of 17 species. Ensifer in New Zealand.
| Ensifer abri | D |
| Sinorhizobium americanum | F |
| Ensifer arboris | |
| Ensifer fredii | formerly Rhizobium fredii, former Type of Sinorhizobium G |
| Ensifer garamanticus | Merabet et al. (2010) |
| Ensifer indiaense | D |
| Ensifer kostiensis | |
| Ensifer kummerowiae | |
| Ensifer medicae | |
| Ensifer meliloti | formerly Rhizobium meliloti |
| Ensifer mexicanus | Lloret et al. (2007) |
| 'Sinorhizobium morelense' | E |
| Ensifer adhaerens | A |
| Ensifer numidicus | Merabet et al. (2010) |
| Ensifer saheli | B |
| Ensifer sojae | Li et al. (in press) |
| Ensifer terangae | C |
A — This name is a earlier heterotypic synonym of Sinorhizobium morelense (see Young, 2003)
B — This species should be called “Sinorhizobium sahelense” in technically correct Latin (referring to Sahel), but according to a note on Rule 61 of the Code, since S. saheli appears on a IJSEM list it cannot be corrected.
C — This species is incorrectly known as Sinorhizobium teranga
D — Although these species have been published (Ogasawara, et al. 2003), they have not yet been included in the "Validation List" of the International Journal of Systematic and Evolutionary Microbiology, and no type strains exist in international culture collections.
E — This name may be a later heterotypic synonym of Ensifer adhaerens Young (2003), or a distict species Martens et al. (2007).
F — Not yet formally renamed as Ensifer.
G — Ensifer xinjiangense is later heterotypic synonym of Ensifer fredii.
Bradyrhizobium
class: Alphaproteobacteria order: Rhizobiales family: Bradyrhizobiaceae
The Bradyrhizobium genus was described by Jordan in 1982. It currently consists of 9 rhizobia species (and 1 non rhizobial species). Bradyrhizobium in New Zealand .
| Bradyrhizobium canariense | |
| Bradyrhizobium cytisi | |
| Bradyrhizobium denitrificans | formerly Blastobacter denitrificans; |
| Bradyrhizobium elkanii | |
| Bradyrhizobium iriomotense | Islam et al. (2008) |
| Bradyrhizobium japonicum | formerly Rhizobium japonicum, Type species |
| Bradyrhizobium jicamae | RamĂrez-Bahena et al. (2009) |
| Bradyrhizobium liaoningense | |
| Bradyrhizobium pachyrhizi | RamĂrez-Bahena et al. (2009) |
| Bradyrhizobium yuanmingense |
Burkholderia
class: Betaproteobacteria order: Burkholderiales family: Burkholderiaceae
The Burkholderia genus currently contains seven named rhizobial members and others as Burkholderia sp. Burkholderia in New Zealand.
| Burkholderia caribensis | |
| Burkholderia cepacia | see note X below |
| Burkholderia mimosarum | |
| Burkholderia nodosa | Chen et al (2007) |
| Burkholderia phymatum | |
| Burkholderia sabiae | Chen et al (2008) |
| Burkholderia tuberum |
X — Note that although Burkholderia cepacia is considered to nodulate by Rasolomampianina et al. (2005) and Vandamme et al. (2002), Vandamme et al. (2007) (chapter 1, page 7) notes that recent experiments revealed that nodA and nif genes are not longer detected on these strains and he suggests that the strains lost the characteristic, or the original observation was based on experimental error.
Phyllobacterium
class: Alphaproteobacteria order: Rhizobiales family: Phyllobacteriaceae
The Phyllobacterium genus currently contains three rhizobial species. Phyllobacterium in New Zealand.
| Phyllobacterium trifolii | |
| Phyllobacterium ifriqiyense | Mantelin et al. (2006) F |
| Phyllobacterium leguminum | Mantelin et al. (2006) F |
F Note: isolated from nodules, but not proven to nodulate.
Microvirga
class: Alphaproteobacteria order: Rhizobiales family: Methylobacteriaceae
The Microvirga genus currently contains three rhizobial species. Microvirga in New Zealand.
| Microvirga lupini | Ardley et al. (in press) |
| Microvirga lotononidis | Ardley et al. (in press) |
| Microvirga zambiensis | Ardley et al. (in press) |
Azorhizobium
class: Alphaproteobacteria order: Rhizobiales family: Hyphomicrobiaceae
The Azorhizobium genus was described by Dreyfus et al. in 1988. It currently consists of 2 species.
| Azorhizobium caulinodans | Type species |
| Azorhizobium doebereinerae | formerly Azorhizobium johannae |
Ochrobactrum
class: Alphaproteobacteria order: Rhizobiales family: Brucellaceae
The Ochrobactrum genus currently contains two rhizobial species. Ochrobactrum in New Zealand.
| Ochrobactrum cytisi | Zurdo-Piñeiro et al. 2007 |
| Ochrobactrum lupini |
Methylobacterium
class: Alphaproteobacteria order: Rhizobiales family: Methylobacteriaceae
The Methylobacterium genus contains only a single rhizobial species. Methylobacterium in New Zealand.
| Methylobacterium nodulans |
Cupriavidus
class: Betaproteobacteria order: Burkholderiales family: Burkholderiaceae
Cupriavidus formerly Wautersia, formerly Ralstonia (some species), has recently undergone several taxonomic revisions. This genus currently contains a single rhizobial species.
| Cupriavidus taiwanensis |
Devosia
class: Alphaproteobacteria order: Rhizobiales family: Hyphomicrobiaceae
The Devosia genus currently contains only a single rhizobial species (and 1 potentially non rhizobial species).
| Devosia neptuniae |
Shinella
class: Alphaproteobacteria order: Rhizobiales family: Rhizobiaceae
The Shinella genus currently contains a single rhizobial species.
| Shinella kummerowiae | Lin et al. (2008) |
References
A general excellent resource is:
List of Prokaryotic names with Standing in Nomenclature (LPSN). Available http://www.bacterio.net.
For the full list of references for each strain, please check my PhD thesis, Table 1.1, page 3. New References added since the publication of my thesis are listed below:
As of 2016 References will be added to the original publication in the column after the species name and doi: link to the paper. Note that this is NOT the authority, just the original publication.