''Ensifer'' (often referred to in literature by its

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

''Sinorhizobium'') is a genus of

nitrogen-fixing Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmos ...

bacteria (

rhizobia Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In gene ...

), three of which (''

Ensifer meliloti ''Ensifer meliloti'' (formerly ''Rhizobium meliloti'' and ''Sinorhizobium meliloti'') are an aerobic, Gram-negative, and diazotrophic species of bacteria. ''S. meliloti'' are motile and possess a cluster of peritrichous flagella. ''S. meliloti' ...

'', ''

Ensifer medicae Ensifer medicae (also known as ''Sinorhizobium medicae'') is a species of gram-negative, nitrogen-fixing, rod-shaped bacteria. They can be free-living or symbionts of leguminous plants in root nodules. ''E.medicae'' was first isolated from roo ...

'' and '' Ensifer fredii'') have been sequenced.

Etymology

The generic epithet ''Ensifer'' derives from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

noun ''ensifer'', "sword-bearer". The synonym ''Sinorhizobium'' is a combination of

Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Western Europe during the Middle Ages. In this region it served as the primary written language, though local languages were also written to varying degrees. Latin functioned ...

noun ''sino'' ("China"), the

Classical Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

noun ''rhiza'' ("root"), and the

noun ''bium'' ("life"). Thus, the Neo-Latin generic epithet of the synonym ''Sinorhizobium'' means "a ''Rhizobium'' isolated from China", in turn referring to the related genus ''

Rhizobium ''Rhizobium'' is a genus of Gram-negative soil bacteria that fix nitrogen. ''Rhizobium'' species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants. The bacteria colonize plant cells ...

'' ("root-associated life form").

Proper name

The name ''Ensifer'' was published in 1982 and the name ''Sinorhizobium'' was published in 1988 thus the latter is regarded as a later synonym and by the rules of the Bacteriological Code (1990 Revision) of the International Committee on Systematics of Prokaryotes (ICSP), the older name (''Ensifer'') takes 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.

Deprecated species

Two species have been described which have since been reclassified into existing species: ''Sinorhizobium morelense'' (now ''Ensifer adhaerens'') and ''Sinorhizobium xinjiangense'' (now '' Ensifer fredii''—though some dissent exists).

Phylogeny

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature ...

(LPSN). The following phylogeny is based on whole-genome analysis. This phylogeny is based on a constrained analysis of the

16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRNA ...

References

{{Taxonbar, from1=Q26208700, from2=Q3605613 Rhizobiaceae Bacteria genera