根瘤菌主要指與豆類作物根部共生形成根瘤並能固氮的細菌，一般指根瘤菌屬和慢生根瘤菌屬；兩屬都屬於根瘤菌目。

根瘤菌侵入寄主根內，刺激根部皮層和中柱鞘的某些細胞，引起這些細胞的強烈生長，使根的局部膨大形成根瘤；根瘤菌在根內定居，植物供給根瘤菌以礦物養料和能源，根瘤菌固定大氣中游離氮氣，為植物提供氮素養料，兩者在拮抗寄生關係中處於均衡狀態而表現共生現象。

根瘤菌細胞呈杆狀，有鞭毛和莢膜，鞭毛為正常的活動器官，無芽孢，革蘭氏染色陰性，屬需氧型。在根瘤中生活的菌體形式多種多樣，有梨形、棍棒型或 T、X、Y 等型，這種變形的菌體成為類菌體；類菌體在豆科植物體內不生長繁殖，卻能與豆科植物共同固氮，對豆科植物有良好作用。

每種根瘤菌只能與一種或幾種植物建立共生關係，如下表：

此外，還有些微生物能同非豆類植物共同形成根瘤固氮，主要是一些放線菌（如：小頭木麻黃、赤楊、楊梅）、藍綠菌（如：蘇鐵、竹柏、滿江紅）。



下屬物種


* 根瘤菌屬 _Rhizobium_ Frank, 1889
  
* 苜蓿根瘤菌
  
* 百脈根瘤菌
  
* _Rhizobium acidisoli_ Román-Ponce et al. 2016
  
* _Rhizobium aegyptiacum_ Shamseldin et al. 2017
  
* _Rhizobium aethiopicum_ Aserse et al. 2017
  
* _Rhizobium aggregatum_ (Hirsch and Müller 1986) Kaur et al. 2011
  
* _Rhizobium alamii_ Berge et al. 2009
  
* _Rhizobium alkalisoli_ Lu et al. 2009，異名
  
* _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 arenae_ Zhang et al. 2017
  
* _Rhizobium arsenicireducens_ Mohapatra et al. 2020
  
* _Rhizobium azibense_ Mnasri _et al. 2014_
  
* _Rhizobium azooxidifex_ Behrendt et al. 2016
  
* _Rhizobium bangladeshense_ Rashid et al. 2015
  
* _Rhizobium binae_ Rashid et al. 2015
  
* _Rhizobium borbori_ Zhang et al. 2011，異名
  
* _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 chutanense_ Huo et al. 2019
  
* _Rhizobium ciceri_ Nour et al. 1994，異名
  
* _Rhizobium daejeonense_ Quan et al. 2005
  
* _Rhizobium dioscoreae_ Ouyabe et al. 2020
  
* _Rhizobium ecuadorense_ Ribeiro et al. 2015
  
* _Rhizobium endolithicum_ Parag et al. 2014
  
* _Rhizobium endophyticum_ López-López et al. 2011
  
* _Rhizobium esperanzae Cordeiro et al. 2017_
  
* _Rhizobium etli_ Segovia et al. 1993
  
* _Rhizobium fabae Tian et al. 2008_
  
* _Rhizobium favelukesii_ Torres Tejerizo et al. 2016
  
* _Rhizobium flavum Gu et al. 2014_
  
* _Rhizobium fredii_ Scholla and Elkan 1984，異名
  
* _Rhizobium freirei_ Dall'Agnol et al. 2013
  
* _Rhizobium galegae Lindström 1989，異名_
  
* _Rhizobium gallicum Amarger et al. 1997_
  
* 格氏根瘤菌 _Rhizobium gei_ Shi _et al. 2016_
  
* _Rhizobium giardinii_ Amarger et al. 1997
  
* _Rhizobium grahamii_ López-López et al. 2012
  
* 海南根瘤菌 _Rhizobium hainanense_ Chen et al. 1997
  
* _Rhizobium halophytocola Bibi_ et al. 2012
  
* _Rhizobium helianthi_ Wei _et al. 2015_
  
* _Rhizobium herbae Ren et al. 2011，異名_
  
* _Rhizobium hidalgonense Yan et al. 2020_
  
* 華氏根瘤菌 _Rhizobium huakuii_ Chen et al. 1991，異名
  
* _Rhizobium huautlense Wang et al. 1998，異名_
  
* _Rhizobium indigoferae Wei_ et al. 2002
  
* _Rhizobium ipomoeae Sheu et al. 2016_
  
* _Rhizobium jaguaris Rincón-Rosales et al. 2013_
  
* _Rhizobium japonicum_ (Kirchner 1896) Buchanan 1926，異名
  
* _Rhizobium laguerreae Saïdi_ et al. 2014
  
* _Rhizobium larrymoorei''_ (Bouzar and Jones 2001) Young 2004，異名
  
* 豌豆根瘤菌 _Rhizobium leguminosarum_ (Frank 1879) Frank 1889
  
* _Rhizobium lemnae Kittiwongwattana and Thawai 2014_
  
* _Rhizobium lentis Rashid et al. 2015_
  
* _Rhizobium leucaenae Ribeiro et al. 2012_
  
* _Rhizobium loessense Wei_ et al. 2003，異名
  
* _Rhizobium loti_ Jarvis et al. 1982，異名
  
* _Rhizobium lupini_ (Schroeter 1886) Eckhardt et al. 1931，異名
  
* _Rhizobium lusitanum_ Valverde et al. 2006
  
* _Rhizobium marinum_ Liu et al. 2015
  
* _Rhizobium mayense_ Rincón-Rosales et al. 2013
  
* _Rhizobium mediterraneum_ Nour et al. 1995，異名
  
* _Rhizobium meliloti_ Dangeard 1926，異名
  
* _Rhizobium mesoamericanum_ López-López et al. 2012
  
* _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 naphthalenivorans_ Kaiya et al. 2018
  
* _Rhizobium nepotum_ Puławska et al. 2012，異名
  
* _Rhizobium oryzae_ Peng et al. 2008，異名
  
* _Rhizobium oryzicola_ Zhang et al. 2015
  
* _Rhizobium oryziradicis_ Zhao et al. 2017，異名
  
* _Rhizobium pakistanense_ corrig. Khalid et al. 2015
  
* _Rhizobium pakistanensis_ Khalid et al. 2015，拼寫錯誤
  
* _Rhizobium paknamense_ Kittiwongwattana and Thawai 2013
  
* _Rhizobium paranaense_ Dall'Agnol et al. 2014
  
* _Rhizobium petrolearium_ Zhang et al. 2012
  
* _Rhizobium phaseoli_ Dangeard 1926
  
* _Rhizobium pisi_ Ramírez-Bahena et al. 2008
  
* _Rhizobium populi_ Rozahon et al. 2014
  
* _Rhizobium pseudoryzae_ Zhang et al. 2011，異名
  
* _Rhizobium puerariae_ Boonsnongcheep et al. 2016
  
* _Rhizobium pusense_ Panday et al. 2011，異名
  
* _Rhizobium radiobacter_ (Beijerinck and van Delden 1902) Young et al. 2001，異名
  
* _Rhizobium rhizogenes_ (Riker et al. 1930) Young et al. 2001
  
* _Rhizobium rhizophilum_ Gao et al. 2020
  
* _Rhizobium rhizoryzae_ Zhang et al. 2014
  
* _Rhizobium rosettiformans_ Kaur et al. 2011
  
* _Rhizobium rubi_ (Hildebrand 1940) Young et al. 2001，異名
  
* _Rhizobium ruizarguesonis_ Jorrin et al. 2020
  
* _Rhizobium selenireducens_ Hunter et al. 2008
  
* _Rhizobium selenitireducens_ corrig. Hunter et al. 2008
  
* _Rhizobium skierniewicense_ Puławska et al. 2012
  
* _Rhizobium smilacinae_ Zhang et al. 2015
  
* _Rhizobium soli_ Yoon et al. 2010
  
* _Rhizobium sophorae_ Jiao et al. 2015
  
* _Rhizobium sophoriradicis_ Jiao et al. 2015
  
* _Rhizobium sphaerophysae_ Xu et al. 2012
  
* _Rhizobium straminoryzae_ Lin et al. 2014
  
* _Rhizobium subbaraonis_ Ramana et al. 2013
  
* _Rhizobium sullae Squartini_ et al. 2002
  
* 太白山根瘤菌 _Rhizobium taibaishanense_ Yao et al. 2012，異名
  
* _Rhizobium tarimense_ Turdahon et al. 2013
  
* 天山根瘤菌 _Rhizobium tianshanense_ Chen et al. 1995，異名
  
* _Rhizobium tibeticum_ Hou et al. 2009
  
* _Rhizobium trifolii_ Dangeard 1926，異名
  
* _Rhizobium tropici_ Martínez-Romero et al. 1991
  
* _Rhizobium tubonense_ Zhang et al. 2011
  
* _Rhizobium tumorigenes_ Kuzmanović et al. 2019
  
* _Rhizobium undicola_ (de Lajudie et al. 1998) Young et al. 2001，異名
  
* _Rhizobium vallis_ Wang et al. 2011
  
* _Rhizobium vignae_ Ren et al. 2011，異名
  
* _Rhizobium viscosum_ (Gasdorf et al. 1965) Flores-Félix et al. 2017
  
* _Rhizobium vitis_ (Ophel and Kerr 1990) Young et al. 2001，異名
  
* _Rhizobium wenxiniae_ Gao et al. 2017
  
* _Rhizobium wuzhouense_ Yuan et al. 2018
  
* _Rhizobium yanglingense_ Tan et al. 2001
  
* _Rhizobium yantingense_ Chen et al. 2015
  
* _Rhizobium zeae_ Celador-Lera et al. 2017

* 慢生根瘤菌屬 _Bradyrhizobium_ Jordan，1982
  
* 大豆慢生根瘤菌 _Bradyrhizobium japonicum_，曾稱為大豆根瘤菌。



參考資料



外部連結


* Current research on _Rhizobium leguminosarum_ （頁面存檔備份，存於網際網路檔案館） at the Norwich Research Park

* Video and commentary on root nodules and Rhizobium in White Clover （頁面存檔備份，存於網際網路檔案館）