Methylovirgula ligni gen. nov., sp. nov., an obligately acidophilic, facultatively methylotrophic bacterium with a highly divergent mxaF gene

1 S. N. Winogradsky Institute of Microbiology, Russian Academy of Sciences, Moscow 117312, Russia 2 Netherlands Institute of Ecology, Centre for Terrestrial Ecology, 6666 ZG Heteren, The Netherlands 3 Netherlands Institute of Ecology, Centre for Limnology, 3631 AC Nieuwersluis, The Netherlands 4 G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow region, 142292, Russia Correspondence Svetlana N. Dedysh dedysh{at}mail.ru Two strains of Gram-negative, aerobic, non-pigmented, non-motile, rod-shaped bacteria were isolated from beechwood blocks during decay by the white-rot fungus Hypholoma fasciculare and were designated strains BW863 T and BW872. They are capable of methylotrophic growth and assimilate carbon via the ribulose-bisphosphate pathway. In addition to methanol, the novel isolates utilized ethanol, pyruvate and malate. Strains BW863 T and BW872 are obligately acidophilic, mesophilic organisms capable of growth at pH 3.1–6.5 (with an optimum at pH 4.5–5.0) and at 4–30 °C. Phospholipid fatty acid profiles of these bacteria contain unusually large amounts (about 90 %) of C 18 : 1 7 c , thereby resembling the profiles of Methylobacterium strains. The predominant quinone is Q-10. The DNA G+C content of the novel isolates is 61.8–62.8 mol%. On the basis of 16S rRNA gene sequence similarity, strains BW863 T and BW872 are most closely related to the acidophilic methanotroph Methylocapsa acidiphila B2 T (96.5–97 %). Comparative sequence analysis of mxaF , the gene encoding the large subunit of methanol dehydrogenase, placed the MxaF sequences of the two novel strains in a cluster that is distinct from all previously described MxaF sequences of cultivated methylotrophs. The identity between the MxaF sequences of the acidophilic isolates and those from known alpha-, beta- and gammaproteobacterial methylotrophs was respectively 69–75, 61–63 and 64–67 %. The data therefore suggest that strains BW863 T and BW872 represent a novel genus and species of methylotrophic bacteria, for which the name Methylovirgula ligni gen. nov., sp. nov. is proposed. Strain BW863 T (=DSM 19998 T =NCIMB 14408 T ) is the type strain of Methylovirgula ligni . Abbreviations: ICM, intracytoplasmic membrane; PLFA, phospholipid fatty acid; PMS, phenazine methosulfate; RuBisCO, ribulose-1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose bisphosphate; SIP, stable-isotope probing The GenBank/EMBL/DDBJ accession numbers f