Rhizobium of alfalfa group is

Rhizobium is a genus of gram-negative soil bacteria that fix nitrogen for plants.
Alfa alfa is an important leguminous forage crop, which is hypothesized to select compatible rhizobial partners from the rhizosphere to form nitrogen-fixing nodules.
Rhizobium of alfalfa group is Melilolti. Meliloti are motile and possess a cluster of peritrichous flagella. It fixes atmospheric nitrogen into ammonia for their legume symbionts.