Singulisphaera rosea sp nov., a planctomycete from acidic Sphagnum peat, and emended description of the genus Singulisphaera

An aerobic, pink-pigmented, budding bacterium, designated strain S26(T), was isolated from an acidic Sphagnum peat bog of north-western Russia. Cells were non-motile and spherical, occurring singly, in pairs or in short chains, and were able to attach to surfaces by means of a holdfast material. Strain S26(T). was a moderately acidophilic, mesophilic organism capable of growth at pH 3.2-7.1 (optimum at pH 4.8-5.0) and at 4-33 degrees C (optimum at 20-26 degrees C). Most sugars, several organic acids and polyalcohols were the preferred growth substrates. The major fatty acids were C-16:0, C-18:1 omega 9c and C-18:2 omega 6c,12c. The major neutral lipids were n-C-31 :9 hydrocarbon and squalene; the polar lipids were phosphatidylglycerol, phosphatidylcholine and components with an unknown structure. The DNA G + C content of strain S26(T) was 62.2 mol%. 16S rRNA gene sequence analysis showed that strain S26(T) is a member of the order Planctomycetales. Among taxonomically characterized representatives of this order, highest levels of 16S rRNA gene sequence similarity (95.1-95.2%) were observed with strains of the non-filamentous, peat-inhabiting planctomycete Singulisphaera acicliphila. Strain S26(T) could be differentiated from Singulisphaera acidiphila based on pigmentation, significant differences in substrate utilization patterns, greater tolerance of acidic conditions and the presence of C-16:1 omega 9c. Based on the data presented, strain S26(T) is considered to represent a novel species of the genus Singulisphaera, for which the name Singulisphaera rosea sp. nov. is proposed; the type strain is S26(T) (=DSM 23044(T)=VKM B-2599(T)).