Rhizobium leguminosarum
| Rhizobium leguminosarum | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Kingdom: | Pseudomonadati |
| Phylum: | Pseudomonadota |
| Class: | Alphaproteobacteria |
| Order: | Hyphomicrobiales |
| Family: | Rhizobiaceae |
| Genus: | Rhizobium |
| Species: | R. leguminosarum |
| Binomial name | |
| Rhizobium leguminosarum (Frank 1879) Frank 1889 (Approved Lists 1980) | |
| Type strain | |
| ATCC 10004[1] LMG 14904 strain 3Hoq18 USDA 2370 | |
| Biovars | |
| |
| Synonyms[1] | |
| |
Rhizobium leguminosarum is a Gram-negative soil bacterium in the genus Rhizobium that forms mutualistic, nitrogen-fixing symbioses with legumes. Compatible strains colonise the roots of various host plants and induce the formation of root nodules, within which the bacteria differentiate into bacteroids and convert atmospheric nitrogen into ammonium compounds that can be used by the plant. In return, the plant supplies the bacteria with carbon compounds.[2]
Different symbiotic groups have characteristic host ranges: strains of symbiovar viciae nodulate legumes including peas, vetches and lentils, whereas symbiovar trifolii is associated with clovers.[3] R. leguminosarum, particularly strains of symbiovar viciae, has been widely used as a model for studying root-nodule formation, bacteroid metabolism and symbiotic nitrogen fixation.[2] Its genome has also been extensively studied, including the complete sequencing of the widely used strain 3841.[4]
Morphology
Rhizobium leguminosarum is a Gram-negative, motile, rod-shaped, aerobic bacterium.[5]
Common biovars
Rhizobium leguminosarum biovar trifolii, and R. leguminosarum biovar viciae are the most commonly studied biovars of R. leguminosarum, with certain studies seemingly treating R. trifolii as its own species.[6]
Symbiosis and nitrogen fixation
The symbiosis between R. leguminosarum and its host plants involves an exchange of chemical signals. Compounds released by legume roots, particularly flavonoids and other phenolic compounds, are detected by rhizobial regulatory proteins such as NodD, which activate bacterial nod genes. These genes direct the production of Nod factors, signalling molecules whose precise chemical structure is an important determinant of host specificity.[7]
In susceptible legumes, Nod-factor signalling causes changes including root hair deformation and curling. The bacteria enter through structures known as infection threads and are delivered into developing root nodules, where they differentiate into bacteroids capable of nitrogen fixation.[7][8] Within the nodule, the plant supplies the bacteroids with carbon compounds, while the bacteria reduce atmospheric nitrogen to forms that can be assimilated by the plant. Nitrogenase is sensitive to oxygen, although the bacteroids require oxygen for respiration; leghemoglobin produced in the nodule helps maintain a low free-oxygen concentration while delivering oxygen to the bacteroids.[9]
Genome
The extensively studied R. leguminosarum bv. viciae strain 3841 has a genome of approximately 7.75 million base pairs, consisting of a circular chromosome and six circular plasmids.[4] Many genes involved in the symbiosis are carried on plasmids. In strain 3841, the 488-kilobase plasmid pRL10 is the principal symbiotic plasmid and contains clustered nod genes required for nodulation together with nif and fix genes involved in nitrogen fixation.[4]
Fatty acid synthesis
Rhizobium leguminosarum's acyl carrier protein differs from most ACPs by having a C-terminus extension. This ACP is also used in the synthesis of unusually long ACPs which themselves are then used in the synthesis of the R. leguminosarum nod factor.[10]
Uses
R. leguminosarum is widely used in the inoculation of legume seeds. The sv. trifolii strain U204 is commercially used to inoculate white and red clover in particular, but better strains for this purpose are being developed.[11]
Research has been carried out into the role that R. leguminosarum could play in promoting growth of canola and lettuce.[12]
References
- 1 2 Euzéby, JP; Parte, AC. "Rhizobium leguminosarum". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved May 28, 2021.
- 1 2 Karunakaran, R.; Ramachandran, V. K.; Seaman, J. C.; East, A. K.; Mouhsine, B.; Mauchline, T. H.; Prell, J.; Skeffington, A.; Poole, P. S. (2009). "Transcriptomic analysis of Rhizobium leguminosarum biovar viciae in symbiosis with host plants Pisum sativum and Vicia cracca". Journal of Bacteriology. 191 (12): 4002–4014. doi:10.1128/JB.00165-09. PMC 2698398. PMID 19376875.
- ↑ Sánchez-Contreras, M.; Bauer, W. D.; Gao, M.; Robinson, J. B.; Downie, J. A. (2007). "Quorum-sensing regulation in rhizobia and its role in symbiotic interactions with legumes". Philosophical Transactions of the Royal Society B. 362 (1483): 1149–1163. doi:10.1098/rstb.2007.2041. PMC 2435579. PMID 17360278.
- 1 2 3 Young, J. Peter W.; Crossman, Lisa C.; Johnston, Andrew W. B. (2006). "The genome of Rhizobium leguminosarum has recognizable core and accessory components". Genome Biology. 7 (4): R34. doi:10.1186/gb-2006-7-4-r34. PMC 1557990. PMID 16640791.
- ↑ "Rhizobium leguminosarum". Biology Online Dictionary. Retrieved 8 December 2015.
- ↑ An, JH; Kim, YS (15 October 1998). "A gene cluster encoding malonyl-CoA decarboxylase (MatA), malonyl-CoA synthetase (MatB) and a putative dicarboxylate carrier protein (MatC) in Rhizobium trifolii--cloning, sequencing, and expression of the enzymes in Escherichia coli". European Journal of Biochemistry. 257 (2): 395–402. doi:10.1046/j.1432-1327.1998.2570395.x. PMID 9826185.
- 1 2 Downie, J. Allan (2010). "The roles of extracellular proteins, polysaccharides and signals in the interactions of rhizobia with legume roots". FEMS Microbiology Reviews. 34 (2): 150–170. doi:10.1111/j.1574-6976.2009.00205.x. PMID 20070373.
- ↑ Gage, Daniel J. (2004). "Infection and invasion of roots by symbiotic, nitrogen-fixing rhizobia during nodulation of temperate legumes". Microbiology and Molecular Biology Reviews. 68 (2): 280–300. doi:10.1128/MMBR.68.2.280-300.2004. PMC 419923. PMID 15187185.
- ↑ Larrainzar, Estíbaliz; Villar, Irene; Rubio, Maria Carmen (2020). "Hemoglobins in the legume–Rhizobium symbiosis". New Phytologist. 228 (2): 472–484. doi:10.1111/nph.16673. hdl:10261/220175. PMID 32442331.
- ↑ White, Stephen W.; Zheng, Jie; Zhang, Yong-Mei; Rock, Charles O. (2005). "The Structural Biology of Type II Fatty Acid Biosynthesis". Annual Review of Biochemistry. 74 (1). Annual Reviews: 791–831. doi:10.1146/annurev.biochem.74.082803.133524. ISSN 0066-4154. PMID 15952903. (COR ORCID 0000-0001-8648-4189).
- ↑ Irisarri, Pilar; Cardozo, Gerónimo; Tartaglia, Carolina; Reyno, Rafael; Gutiérrez, Pamela; Lattanzi, Fernando A.; Rebuffo, Mónica; Monza, Jorge (23 April 2019). "Selection of Competitive and Efficient Rhizobia Strains for White Clover". Frontiers in Microbiology. 10 768. doi:10.3389/fmicb.2019.00768. PMC 6489563. PMID 31065250.
- ↑ Noel, TC; Sheng, C; Yost, CK; Pharis, RP; Hynes, MF (March 1996). "Rhizobium leguminosarum as a plant growth-promoting rhizobacterium: direct growth promotion of canola and lettuce". Canadian Journal of Microbiology. 42 (3): 279–83. doi:10.1139/m96-040. PMID 8868235.
External links