Zavarzinella formosa gen. nov., sp. nov., a novel stalked, Gemmata-like planctomycete from a Siberian peat bog

An aerobic, pink-pigmented, budding and rosette-forming bacterium was isolated from an acidic Sphagnum peat bog and designated strain A10(T). The 16S rRNA gene sequence analysis showed that strain A10(T) was a member of the order Planctomycetales and belonged to a phylogenetic lineage defined by the genus Gemmata, with 90% sequence similarity to that of Gemmata obscuriglobus, the only taxonomically described organism of this group. Ellipsoid-shaped cells of strain A10(T) were uniformly covered with crateriform pits and possessed long (up to 10-15 mu m) and unusually thick (0.5-0.7 mu m) stalks of a unique ultrastructure. Thin sections revealed a complex intracellular membrane system compartmentalizing the cells. Strain A10(T) was a moderately acidophilic, mesophilic organism capable of growth at pH values between 3.8 and 7.2 (with an optimum at pH 5.5-6.0) and at temperatures between 10 and 30 degrees C (with an optimum at 20-25 degrees C). The major fatty acids were C-18:0, C-18:1 omega 5c and C-16:1 omega 5c and the major quinone was MK-6. Cells of strain A10(T) contained high amounts of bound saturated and monounsaturated C-26-C-32 (omega-1) hydroxy fatty acids. The G+C content of the DNA was 62.5 mol%. The unique cell morphology, the capability of growth in acidic conditions and a number of chemotaxonomic and genotypic characteristics served to differentiate strain A10(T) from G. obscuriglobus. Based on these data, the novel isolate should be considered as representing a novel genus and species of planctomycetes, for which the name Zavarzinella formosa gen. nov., sp. nov. is proposed The type strain is A10(T) (= DSM 19928(T) =VKM B-2478(T)).