Rhizobium

Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium species form an endosymbiotic nitrogen-fixing association with roots of 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 compounds 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 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. 2016Rhizobium aegyptiacum Shamseldin et al. 2016Rhizobium aethiopicum Aserse et al. 2017Rhizobium alamii Berge et al. 2009

"Rhizobium album" Hang et al. 2019
"Rhizobium albus" Li et al. 2017Rhizobium altiplani Baraúna et al. 2016Rhizobium alvei Sheu et al. 2015Rhizobium anhuiense Zhang et al. 2015Rhizobium aquaticum Máthé et al. 2019
"Rhizobium arachis" Wang et al. 2001Rhizobium arenae Zhang et al. 2017Rhizobium arsenicireducens Mohapatra et al. 2020Rhizobium azooxidifex Behrendt et al. 2016Rhizobium bangladeshense Rashid et al. 2015Rhizobium binae Rashid et al. 2015Rhizobium calliandrae Rincón-Rosales et al. 2013Rhizobium capsici Lin et al. 2015Rhizobium cauense Liu et al. 2015Rhizobium cellulosilyticum García-Fraile et al. 2007Rhizobium changzhiense Zhang et al. 2021Rhizobium chutanense Huo et al. 2019
"Rhizobium cremeum" Yang et al. 2022
"Rhizobium croatiense" Rajnovic et al. 2022
"Rhizobium deserti" Liu et al. 2020Rhizobium dioscoreae Ouyabe et al. 2020Rhizobium ecuadorense Ribeiro et al. 2015Rhizobium endophyticum López-López et al. 2010Rhizobium esperanzae Cordeiro et al. 2017Rhizobium etli Segovia et al. 1993Rhizobium favelukesii Torres Tejerizo et al. 2016
"Rhizobium flavescens" Su et al. 2021Rhizobium freirei Dall'Agnol et al. 2013Rhizobium gallicum Amarger et al. 1997Rhizobium gei Shi et al. 2016
"Rhizobium glycinendophyticum" Wang et al. 2020Rhizobium grahamii López-López et al. 2011Rhizobium hainanense Chen et al. 1997Rhizobium 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. 1984Rhizobium helianthi Wei et al. 2015Rhizobium hidalgonense Yan et al. 2020
"Rhizobium indicum" Rahi et al. 2020Rhizobium indigoferae Wei et al. 2002Rhizobium jaguaris Rincón-Rosales et al. 2013
"Rhizobium kunmingense" Shen et al. 2010Rhizobium laguerreae Saïdi et al. 2014Rhizobium leguminosarum Frank 1889 Rhizobium lemnae Kittiwongwattana & Thawai 2014Rhizobium lentis Rashid et al. 2015Rhizobium leucaenae Ribeiro et al. 2011Rhizobium lusitanum Valverde et al. 2006
"Candidatus Rhizobium massiliense" Greub et al. 2004.Rhizobium mayense Rincón-Rosales et al. 2013Rhizobium mesoamericanum López-López et al. 2011Rhizobium mesosinicum Lin et al. 2009Rhizobium metallidurans Grison et al. 2015Rhizobium miluonense Gu et al. 2008Rhizobium mongolense van Berkum et al. 1998Rhizobium multihospitium Han et al. 2008Rhizobium oryzicola Zhang et al. 2015
"Rhizobium oryzihabitans" Zhao et al. 2020Rhizobium pakistanense corrig. Khalid et al. 2015
"Rhizobium panacihumi" Kang et al. 2019Rhizobium paranaense Dall'Agnol et al. 2014Rhizobium phaseoli Dangeard 1926
"Rhizobium phenanthrenilyticum" Wen et al. 2011Rhizobium pisi Ramírez-Bahena et al. 2008
"Rhizobium pongamiae" Kesari et al. 2013Rhizobium populi Rozahon et al. 2014
"Rhizobium populisoli" Shen et al. 2021Rhizobium puerariae Boonsnongcheep et al. 2016
"Rhizobium qilianshanense" Xu et al. 2013
"Rhizobium quercicola" Wang et al. 2022
"Rhizobium redzepovicii" Rajnovic et al. 2022Rhizobium rhizogenes Young et al. 2001
"Rhizobium rhizolycopersici" Thin et al. 2021Rhizobium rhizoryzae Zhang et al. 2014Rhizobium ruizarguesonis Jorrin et al. 2020Rhizobium smilacinae Zhang et al. 2014Rhizobium soli Yoon et al. 2010Rhizobium sophorae Jiao et al. 2014Rhizobium sophoriradicis Jiao et al. 2014Rhizobium straminoryzae Lin et al. 2014Rhizobium sullae Squartini et al. 2002
"Rhizobium terrae" Ruan et al. 2020Rhizobium tibeticum Hou et al. 2009Rhizobium tropici Martínez-Romero et al. 1991Rhizobium tubonense Zhang et al. 2011Rhizobium tumorigenes Kuzmanović et al. 2019Rhizobium vallis Wang et al. 2011Rhizobium viscosum Flores-Félix et al. 2017Rhizobium wenxiniae Gao et al. 2017Rhizobium yanglingense Tan et al. 2001Rhizobium zeae Celador-Lera et al. 2017

Species in "double quotes" 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. The phylogeny is based on whole-genome analysis.