|Sinorhizobium fredii strain USDA257 on an agar plate.|
Chen et al. 1988/Casida 1982
|Sinorhizobium fredii/Ensifer adhaerens|
Sinorhizobium/Ensifer is a genus of nitrogen-fixing bacteria (rhizobia), three of which (Sinorhizobium meliloti, Sinorhizobium medicae and Sinorhizobium fredii) have been sequenced.
Sinorhizobium is a combination of Medieval Latin sino (which means "China"), Greek rhizo (which means "root"), and New Latin bios (which means "life"). Thus, the generic name means "a bacterium living in a root in China". The other name is from the New Latin term ensifer, which means "sword-bearing" or "sword-bearer".
The name Ensifer was published in 1982 and the name Sinorhizobium was published in 1988. By the rules of the Bacteriological Code (1990 Revision) of the International Committee on Systematics of Prokaryotes (ICSP), the older name (Ensifer) has priority. In response to a request that the single extant species of Ensifer (Ensifer adhaerens) be moved to Sinorhizobium, a special ICSP subcommittee was formed to evaluate the request. It was ultimately ruled that Ensifer retained priority and that all Sinorhizobium species be transferred to the genus Ensifer. However, both terms continue to be used in published scientific literature, with Sinorhizobium being the more common.
Two species have been described which have since been reclassified into existing species: Sinorhizobium morelense (now Ensifer adhaerens) and Sinorhizobium xinjiangense (now Sinorhizobium fredii—though some dissent exists).
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)  and National Center for Biotechnology Information (NCBI) and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project