Methylorubrum extorquens AM1

Methylorubrum extorquens AM1 is a laboratory bacterial strain used to investigate methylotrophy, the use of reduced one-carbon compounds such as methanol. The ATCC collection identifies AM1 with deposit ATCC 14718 and designation NCIB 9133. It explicitly marks this as not the type strain. A widely used experimental strain and the reference that anchors a species name need not be the same culture.^[ref]

AM1 makes a metabolic hypothesis testable. In a 2005 study, an AM1-derived mutant lacking functional methanol dehydrogenase could not perform the usual first oxidation from methanol to formaldehyde. Researchers compared its colonization of Medicago truncatula with that of a fluorescently marked reference derivative. The mutant was disadvantaged in competition, yet separately inoculated mutants could reach populations comparable to the wild type. Methanol utilization therefore contributed to competitive success without being indispensable for colonization in that experiment.^[ref]

For a distinct illustrative calculation, suppose both populations start at $10^4$ cells, but finish at $4\times 10^4$ and $1.6\times 10^5$. Both grew, yet the first population's fraction fell from $1/2$ to $1/5$. A declining competitive fraction is thus compatible with an increasing absolute population. The reference, mutant, host and measured quantity all belong to the meaning of an AM1 experimental result.