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

1 S. N. Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-letya Octyabrya 7/2, Moscow 117312, Russia 2 M. V. Lomonosov Moscow State University, Faculty of Biology Science, GSP-2, Leninskie Gory, Moscow 119992, Russia 3 Netherlands Institute of Ecology, NL-3631 AC Nieuwersluis, The Netherlands 4 NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, PO Box 59, NL-1790 AB Den Burg, The Netherlands Correspondence Svetlana N. Dedysh dedysh{at}mail.ru 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 µm) and unusually thick (0.5–0.7 µm) 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 °C (with an optimum at 20–25 °C). The major fatty acids were C 18 : 0 , C 18 : 1 5 c and C 16 : 1 5 c and the major quinone was MK-6. Cells of strain A10 T contained high amounts of bound saturated and monounsaturated C 26 –C 32 ( -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 ). Abbreviations: PLFA, phospholipid fatty acid The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain A10 T is AM162406 . A comparison of the fatty acid compositions of strain A10 T and Gemmata obscuriglobus DSM 5831 T and electron micrographs of negatively stained preparations of cells of strain A10 T are