Bradyrhizobium

Bradyrhizobium is a genus of Gram-negative soil bacteria that naturally occur as free-living soil bacteria or in symbiotic relationships with legumes. Bradyrhizobium is known for nitrogen fixation, which converts atmospheric nitrogen into ammonia (N₂ - NH₃). This process allows plants and other organisms to use organic compounds, such as nitrates, more readily. Nitrogen-fixing bacteria such as Bradyrhizobium are crucial to chemical cycles in the soil.

Microbiology

Ecology

Bradyrhizobium species are Gram-negative, rod-shaped (also called bacilli) with a flagella (like a tail) to help them move through their environment. Gram-negative bacteria are smaller types of bacteria with thin cell walls that are sensitive to drought or water stress. They are commonly found in the soil where they can form relationships with plant roots such as peas, clover, and other legumes in a mutually beneficial, or symbiotic, relationship. In exchange for their nitrogen fixation, the Bradyrhizobium benefit from carbohydrates made by the plant. They are also common in forest soils, although these species tend not to fix nitrogen.

Taxonomy

Accepted species

Bradyrhizobium genus comprises the following species:

• B. agreste Klepa et al. 2021
• B. algeriense Ahnia et al. 2019
• B. americanum Ramírez-Bahena et al. 2017
• B. amphicarpaeae Bromfield et al. 2019
• B. arachidis Wang et al. 2013
• B. archetypum Helene et al. 2020
• B. australiense Helene et al. 2020
• B. betae Rivas et al. 2004
• B. cajani Araújo et al. 2017
• B. canariense Vinuesa et al. 2005
• B. centrosematis corrig. Ramírez-Bahena et al. 2017
• B. cosmicum Wasai-Hara et al. 2020
• B. cytisi Chahbourne et al. 2011
• B. daqingense Wang JY et al. 2012
• B. denitrificans (Hirsch and Müller 1986) van Berkum et al. 2011
• B. diazoefficiens Delamuta et al 2013
• B. diversitatis Serenato Klepa et al. 2021
• B. elkanii Kuykendall et al. 1993
• B. embrapense Delamuta et al.2015
• B. erythrophlei Yao et al. 2015
• B. ferriligni Yao et al. 2015
• B. frederickii de Oliveira Urquiaga et al. 2019
• B. ganzhouense Lu et al. 2014
• B. glycinis Serenato Klepa et al. 2021
• B. guangdongense Li et al. 2015
• B. guangxiense Li et al. 2015
• B. hipponense Rejili et al. 2020
• B. huanghuaihaiense Zhang et al. 2012
• B. icense Durán et al. 2014
• B. ingae da Silva et al. 2014
• B. iriomotense Islam et al. 2010
• B. ivorense Fossou et al. 2020
• B. japonicum (Kirchner 1896) Jordan 1982
  • symbiovar genistearum
  • symbiovar glycinearum
• B. jicamae Ramírez-Bahena et al. 2009
• B. kavangense Lasse gronemeyer et al. 2015
• B. lablabi Chang et al. 2011
• B. liaoningense Xu et al. 1995
• B. lupini Peix et al. 2015
• B. manausense Silva et al. 2014
• B. mercantei Helene et al. 2017
• B. murdochi Helene et al. 2020
• B. namibiense Grönemeyer et al. 2017
• B. nanningense Li et al. 2020
• B. neotropicale Zilli et al. 2014
• B. niftali Klepa et al. 2019
• B. nitroreducens Jang et al. 2020
• B. oligotrophicum (Ohta and Hattori 1985) Ramírez-Bahena et al. 2013
• B. ottawaense Yu et al. 2014
• B. pachyrhizi Ramírez-Bahena et al. 2009
• B. paxllaeri Durán et al. 2014
• B. retamae Guerrouj et al. 2013
• B. rifense Chahboune et al. 2012
• B. ripae Bünger et al. 2018
• B. shewense Aserse et al. 2018
• B. stylosanthis Marçon Delamuta et al. 2016
• B. subterraneum Gronemeyer et al. 2015
• B. symbiodeficiens Bromfield et al. 2020
• B. tropiciagri Delamuta et al. 2015
• B. vignae Grönemeyer et al. 2016
• B. viridifuturi Helene et al. 2015
• B. yuanmingense Yao et al. 2002

Provisional Species

The following species have been published, but not validated according to the Bacteriological Code

• "B. brasilense" Martins da Costa et al. 2017
• "B. campsiandrae" Cabral Michel et al. 2021
• "B. centrolobii" Michel et al. 2017
• "B. forestalis" Martins da Costa et al. 2018
• "B. guangzhouense" Li et al. 2019
• "B. macuxiense" Michel et al. 2017
• "B. sacchari" de Matos et al. 2017
• "Photorhizobium thompsonianum" Eaglesham et al. 1990
• "B. uaiense" Cabral Michel et al. 2020
• "B. valentinum" Durán et al. 2014
• "B. zhanjiangense" Li et al. 2019