Demethylated hopanoids in ‘Ca. Methylomirabilis oxyfera’ as biomarkers for environmental nitrite-dependent methane oxidation

•Unique demethylated hopanoids in ‘Ca. M. oxyfera’ likely directly biosynthesized.•Found potential candidate genes responsible for demethylation of hopanoids.•Multiple reaction monitoring method for detection of demethylated hopanoids.•New perspectives on the sources of demethylated hopanoids.