Methyloraptor flagellatus gen. nov., sp. nov., novel Ancalomicrobiaceae-affiliated facultatively methylotrophic bacteria that feed on methanotrophs of the genus Methylococcus

A morphologically conspicuous microbial association was detected in a bioreactor running in a continuous mode with methanotrophic bacteria of the genus Methylococcus and natural gas as a growth substrate. The association consisted of spherical Methylococcus cells colonized by elongated rods, which produced rosette-like aggregates and inhibited the cultivation process. An isolate of these bacteria, strain S20^T, was obtained and identified as belonging to the alphaproteobacterial family Ancalomicrobiaceae but displaying only a distant relationship (93.9-95.1 % 16S rRNA gene sequence similarity) to characterized members of this family. Strain S20^T was represented by aerobic, motile, facultatively methylotrophic bacteria, which grew between 10 and 45 °C (optimum 30-35 °C) in a pH range of 4.5-8.5 (optimum pH 6.0). These bacteria were capable of attaching to Methylococcus cells and breaking the integrity of methanotroph cell walls, presumably to feed on methanol. The same interaction was observed with Methylomonas species. The finished genome sequence of strain S20^T consisted of a 5.0 Mb chromosome and one plasmid, 0.26 Mb in size; the DNA G + C content was 68.4 %. The genome encoded 3 rRNA operons and ∼ 4400 proteins including MxaFI- and XoxF-like methanol dehydrogenases, all enzymes of the serine pathway as well as a complete chemotaxis pathway, a unipolar polysaccharide adhesin, and a wide range of peptidases. The genome sequence displayed 67.20-69.56 % average amino acid identity to those of earlier described Ancalomicrobiaceae species. We propose to classify these bacteria as representing a novel genus and species, Methyloraptor flagellatus gen. nov., sp. nov., with the type strain S20^T (=KCTC 8649^T = VKM B-3853^T).