Tautonia sociabilis gen. Nov., sp. nov., a novel thermotolerant planctomycete, isolated from a 4000 m deep subterranean habitat

A novel aerobic bacterium, designated as strain GM2012^T, was isolated from a microbial mat proliferating under the flow of thermal water dissipating from the wall of a 4000 m deep mine in South Africa. The cells were non-motile cocci, capable of budding, occurred in single or gathered in aggregates. The organism is a strictly aerobic chemoorganoheterotroph, preferring simple sugars and polysaccharides as growth substrates. The optimal growth occurred at 42^° C and pH 7.5–7.7. The predominant fatty acids were palmitate, stearate and oleate. The G+C content of the DNA was 70.1 mol%. The 16S rRNA gene sequence analysis placed strain GM2012^T within the family Isosphaeraceae of the order Planctomycetales with 88– 89 % sequence identity to Isosphaera pallida, Aquisphaera giovannonii, Singulisphaera acidiphila, Paludisphaera borealis and Tundrisphaera lichenicola type strains. Based on the genotypic and phenotypic distinctive features of the new strain, we propose a novel genus and species Tautonia sociabilis gen. nov., sp. nov. with the type strain GM2012^T (=VKM B-2860,=KCTC 72013).