Sinorhizobium meliloti

Sinorhizobium meliloti is a Gram-negative nitrogen-fixing bacterium (rhizobium). It forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis results in a new plant organ termed a root nodule. The S. meliloti genome contains three replicons: a chromosome (~3.7 megabases) and two chromids, pSymA (~1.4 megabases) and pSymB (~1.7 megabases). Five S. meliloti genomes have been sequenced to date: Rm1021, AK83, BL225C, Rm41, and SM11