Tepidisphaera mucosa gen. nov., sp. nov., a moderately thermophilic member of the class Phycisphaerae in the phylum Planctomycetes, and proposal of a new family, Tepidisphaeraceae fam. nov., and a new order, Tepidisphaerales ord. nov.

Three strains of facultatively aerobic, moderately thermophilic bacteria were isolated from terrestrial hot springs in Baikal Lake region and Kamchatka (Russia). Cells of the new isolates were cocci reproducing by binary fission. The temperature range for growth was between 20 and 56 °C and the pH range for growth from pH 4.5 to 8.5, with optimal growth at 47-50 °C and pH 7.0-7.5. The organisms were chemoheterotrophs preferring sugars and polysaccharides as growth substrates. 16S rRNA gene sequences of strains 2842, 2813 and 2918Kr were nearly identical (99.7-100 % similarity) and indicated that the strains belonged to the phylum Planctomycetes. The phylogenetically closest cultivated relatives were Algisphaera agarilytica 06SJR6-2(T) and Phycisphaera mikurensis FYK2301M01(T) with 16S rRNA gene sequence similarity values of 82.4 and 80.3 %, respectively. The novel strains differed from them by higher growth temperature, sensitivity to NaCl concentration above 3.0 % and by their cellular fatty acids profile. On the basis of phylogenetic and physiological data, strains 2842(T), 2813 and 2918Kr represent a novel genus and species for which we propose the name Tepidisphaera mucosa sp. nov. The type strain is 2842(T) ( = VKM B-2832(T) = JCM 19875(T)). We also propose that Tepidisphaera gen. nov. is the type genus of a novel family, Tepidisphaeraceae fam. nov. and a novel order, Tepidisphaerales ord. nov.