A novel Methylomirabilota methanotroph potentially couples methane oxidation to iodate reduction

Methane oxidizing microbes play a key role in reducing the emission of this potent greenhouse gas to the atmosphere. The known versatility of the recently discovered anaerobic Methylomirabilota methanotrophs is limited. Here, we report a novel uncultured Methylomirabilis species, Candidatus Methylomirabilis iodofontis, with the genetic potential of iodate respiration from biofilm in iodine-rich cavern spring water. Star-like cells resembling Methylomirabilis oxyfera were directly observed from the biofilm and a high-quality metagenome-assembled genome (MAG) of Ca. M. iodofontis was assembled. In addition to oxygenic denitrification and aerobic methane oxidation pathways, the M. iodofontis MAG also indicated its iodate-reducing potential, a capability that would enable the bacterium to use iodate other than nitrite as an electron acceptor, a hitherto unrecognized metabolic potential of Methylomirabilota methanotrophs. The results advance the current understanding of the ecophysiology of anaerobic Methylomirabilota methanotrophs and may suggest an additional methane sink, especially in iodate-rich ecosystems.