''Rhizobium'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of Gram-negative

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

that fix nitrogen. ''Rhizobium'' species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants. The bacteria colonize plant cells to form root nodules, where they convert atmospheric nitrogen into ammonia using the enzyme nitrogenase. The ammonia is shared with the host plant in the form of organic nitrogenous compounds such as glutamine or ureides. The plant, in turn, provides the bacteria with

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s made by photosynthesis. This mutually beneficial relationship is true of all of the rhizobia, of which the genus ''Rhizobium'' is a typical example. ''Rhizobium'' is also capable of solubilizing phosphate.

History

Martinus Beijerinck was the first to isolate and cultivate a

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

from the nodules of legumes in 1888. He named it ''Bacillus radicicola'', which is now placed in '' Bergey's Manual of Determinative Bacteriology'' under the genus ''Rhizobium''.

Research

''Rhizobium'' forms a symbiotic relationship with certain plants, such as legumes, fixing nitrogen from the air into ammonia, which acts as a natural fertilizer for the plants. The Agricultural Research Service is conducting research involving the genetic mapping of various rhizobial species with their respective symbiotic plant species, like alfalfa or soybean. The goal of this research is to increase the plants' productivity without using fertilizers. In molecular biology, ''Rhizobium'' has been identified as a contaminant of DNA extraction kit reagents and ultrapure water systems, which may lead to its erroneous appearance in microbiota or metagenomic datasets. The presence of nitrogen-fixing bacteria as contaminants may be due to the use of nitrogen gas in ultra-pure water production to inhibit microbial growth in storage tanks.

Species

The genus ''Rhizobium'' comprises the following species:- * '' Rhizobium acidisoli'' Román-Ponce ''et al''. 2016 * '' Rhizobium aegyptiacum'' Shamseldin ''et al''. 2016 * '' Rhizobium aethiopicum'' Aserse ''et al''. 2017 * '' Rhizobium alamii'' Berge ''et al''. 2009 * "'' Rhizobium album''" Hang ''et al''. 2019 * "'' Rhizobium albus''" Li ''et al''. 2017 * '' Rhizobium altiplani'' Baraúna ''et al''. 2016 * '' Rhizobium alvei'' Sheu ''et al''. 2015 * '' Rhizobium anhuiense'' Zhang ''et al''. 2015 * '' Rhizobium aquaticum'' Máthé ''et al''. 2019 * "'' Rhizobium arachis''" Wang et al. 2001 * '' Rhizobium arenae'' Zhang ''et al''. 2017 * '' Rhizobium arsenicireducens'' Mohapatra ''et al''. 2020 * '' Rhizobium azooxidifex'' Behrendt ''et al''. 2016 * '' Rhizobium bangladeshense'' Rashid ''et al''. 2015 * '' Rhizobium binae'' Rashid ''et al''. 2015 * '' Rhizobium calliandrae'' Rincón-Rosales ''et al''. 2013 * '' Rhizobium capsici'' Lin ''et al''. 2015 * '' Rhizobium cauense'' Liu ''et al''. 2015 * '' Rhizobium cellulosilyticum'' García-Fraile ''et al''. 2007 * '' Rhizobium changzhiense'' Zhang ''et al''. 2021 * '' Rhizobium chutanense'' Huo ''et al''. 2019 * "'' Rhizobium cremeum''" Yang et al. 2022 * "'' Rhizobium croatiense''" Rajnovic et al. 2022 * "'' Rhizobium deserti''" Liu ''et al''. 2020 * '' Rhizobium dioscoreae'' Ouyabe ''et al''. 2020 * '' Rhizobium ecuadorense'' Ribeiro ''et al''. 2015 * '' Rhizobium endophyticum'' López-López ''et al''. 2010 * '' Rhizobium esperanzae'' Cordeiro ''et al''. 2017 * '' Rhizobium etli'' Segovia ''et al''. 1993 * '' Rhizobium favelukesii'' Torres Tejerizo ''et al''. 2016 * "'' Rhizobium flavescens''" Su ''et al''. 2021 * '' Rhizobium freirei'' Dall'Agnol ''et al''. 2013 * '' Rhizobium gallicum'' Amarger ''et al''. 1997 * '' Rhizobium gei'' Shi ''et al''. 2016 * "'' Rhizobium glycinendophyticum''" Wang ''et al''. 2020 * '' Rhizobium grahamii'' López-López ''et al''. 2011 * '' Rhizobium hainanense'' Chen ''et al''. 1997 * '' Rhizobium halophytocola'' Bibi ''et al''. 2012 * "'' Rhizobium halotolerans''" Diange and Lee 2013 * "'' Rhizobium hedysari''" Casella ''et al.'' 1986 * "'' Rhizobium hedysari''" Xu ''et al''. 2017 * "'' Rhizobium hedysarum''" Casella et al. 1984 * '' Rhizobium helianthi'' Wei ''et al''. 2015 * '' Rhizobium hidalgonense'' Yan ''et al''. 2020 * "'' Rhizobium indicum''" Rahi ''et al''. 2020 * '' Rhizobium indigoferae'' Wei ''et al''. 2002 * '' Rhizobium jaguaris'' Rincón-Rosales ''et al''. 2013 * "'' Rhizobium kunmingense''" Shen ''et al''. 2010 * '' Rhizobium laguerreae'' Saïdi ''et al''. 2014 * '' Rhizobium leguminosarum'' (Frank 1879) Frank 1889 (Approved Lists 1980) * '' Rhizobium lemnae'' Kittiwongwattana & Thawai 2014 * '' Rhizobium lentis'' Rashid ''et al''. 2015 * '' Rhizobium leucaenae'' Ribeiro ''et al''. 2011 * '' Rhizobium lusitanum'' Valverde ''et al''. 2006 * "''Candidatus'' Rhizobium massiliense" Greub ''et al''. 2004. * '' Rhizobium mayense'' Rincón-Rosales ''et al''. 2013 * '' Rhizobium mesoamericanum'' López-López ''et al''. 2011 * '' Rhizobium mesosinicum'' Lin ''et al''. 2009 * '' Rhizobium metallidurans'' Grison ''et al''. 2015 * '' Rhizobium miluonense'' Gu ''et al''. 2008 * '' Rhizobium mongolense'' van Berkum ''et al''. 1998 * '' Rhizobium multihospitium'' Han ''et al''. 2008 * '' Rhizobium oryzicola'' Zhang ''et al''. 2015 * "'' Rhizobium oryzihabitans''" Zhao ''et al''. 2020 * '' Rhizobium pakistanense'' corrig. Khalid ''et al''. 2015 * "'' Rhizobium panacihumi''" Kang ''et al''. 2019 * '' Rhizobium paranaense'' Dall'Agnol ''et al''. 2014 * '' Rhizobium phaseoli'' Dangeard 1926 (Approved Lists 1980) * "'' Rhizobium phenanthrenilyticum''" Wen ''et al''. 2011 * '' Rhizobium pisi'' Ramírez-Bahena ''et al''. 2008 * "'' Rhizobium pongamiae''" Kesari ''et al''. 2013 * '' Rhizobium populi'' Rozahon ''et al''. 2014 * "'' Rhizobium populisoli''" Shen et al. 2021 * '' Rhizobium puerariae'' Boonsnongcheep ''et al''. 2016 * "'' Rhizobium qilianshanense''" Xu ''et al''. 2013 * "'' Rhizobium quercicola''" Wang et al. 2022 * "'' Rhizobium redzepovicii''" Rajnovic et al. 2022 * '' Rhizobium rhizogenes'' (Riker ''et al''. 1930) Young ''et al''. 2001 * "'' Rhizobium rhizolycopersici''" Thin ''et al''. 2021 * '' Rhizobium rhizoryzae'' Zhang ''et al''. 2014 * '' Rhizobium ruizarguesonis'' Jorrin ''et al''. 2020 * '' Rhizobium smilacinae'' Zhang ''et al''. 2014 * '' Rhizobium soli'' Yoon ''et al''. 2010 * '' Rhizobium sophorae'' Jiao ''et al''. 2014 * '' Rhizobium sophoriradicis'' Jiao ''et al''. 2014 * '' Rhizobium straminoryzae'' Lin ''et al''. 2014 * '' Rhizobium sullae'' Squartini ''et al''. 2002 * "'' Rhizobium terrae''" Ruan ''et al''. 2020 * '' Rhizobium tibeticum'' Hou ''et al''. 2009 * '' Rhizobium tropici'' Martínez-Romero ''et al''. 1991 * '' Rhizobium tubonense'' Zhang ''et al''. 2011 * '' Rhizobium tumorigenes'' Kuzmanović ''et al''. 2019 * '' Rhizobium vallis'' Wang ''et al''. 2011 * '' Rhizobium viscosum'' (Gasdorf ''et al''. 1965) Flores-Félix ''et al''. 2017 * '' Rhizobium wenxiniae'' Gao ''et al''. 2017 * '' Rhizobium yanglingense'' Tan ''et al''. 2001 * '' Rhizobium zeae'' Celador-Lera ''et al''. 2017 Species in "parentheses" have been described, but not validated according to the Bacteriological Code.

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclatu ...

(LPSN). The phylogeny is based on whole-genome analysis.

Notes

References

External links

Current research on nitrogen fixation by rhizobia
at the Norwich Research Park
Video and commentary on root nodules and Rhizobium in White Clover
{{Authority control Rhizobiaceae Bacteria genera