 Methylorubrum extorquens

Methylorubrum extorquens is a species of bacteria and the type species of Methylorubrum. The older combination Methylobacterium extorquens names the same species: LPSN records it as a homotypic synonym, meaning that the two names share a nomenclatural type.^[ref] Experimental results still need a specified bacterial strain; a species name alone does not identify every tested culture.

Methylorubrum extorquens AM1 is a model for facultative methylotrophy. Its studied pathway converts methanol to formaldehyde, with carbon subsequently divided between oxidation toward carbon dioxide and carbon assimilation into cellular material.^[ref]

A 2005 experiment compared AM1-derived mutants with a reference strain during colonization of Medicago truncatula. Mutants defective in methylotrophy lost ground in competition, yet could reach comparable populations when tested separately. This distinction supports a competitive advantage from methanol use without making it the only usable carbon source.^[ref] In an illustrative count, a population share changing from $1/2$ to $1/4$ halves the strain's share; it does not show that its absolute number of cells halved. Both the fraction and the total count are needed to distinguish relative success from population decline.