Carbon stable isotope patterns of cyclic terpenoids: A comparison of cultured alkaliphilic aerobic methanotrophic bacteria and methane-seep environments

•δ13C composition of cyclic terpenoids of M. kenyense and M. alcaliphilum is reported.•Average Δδ13Cterpenoid-methane is −25‰ for M. kenyense and −16‰ for M. alcaliphilum.•13C-depleted tetrahymanol is a biomarker of aerobic methanotrophs at seeps.•Δδ13Cterpenoid-methane characterizes types of aerobic methanotrophy at seeps.