Psychrophilic sulfate-reducing bacteria isolated from permanently cold Arctic marine sediments: description of Desulfofrigus oceanense gen. nov., sp. nov., Desulfofrigus fragile sp. nov., Desulfofaba gelida gen. nov., sp. nov., Desulfotalea psychrophila gen. nov., sp. nov. and Desulfotalea arctica sp. nov

Max-Planck-Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany Author for correspondence: Christian Knoblauch. Tel: +49 421 2028 653. Fax: +49 421 2028 690. e-mail: cknoblau{at}mpi-bremen.de ABSTRACT Five psychrophilic Gram-negative, sulfate-reducing bacteria were isolated from marine sediments off the coast of Svalbard. All isolates grew at the in situ temperature of -1·7 °C. In batch cultures, strain PSv29 T had the highest growth rate at 7 °C strains ASv26 T and LSv54 T had the highest growth rate at 10 °C, and strains LSv21 T and LSv514 T had the highest growth rate at 18 °C. The new isolates used the most common fermentation products in marine sediments, such as acetate, propionate, butyrate, lactate and hydrogen, but only strain ASv26 T was able to oxidize fatty acids completely to CO 2 . The new strains had growth optima at neutral pH and marine salt concentration, except for LSv54 T which grew fastest with 1% NaCl. Sulfite and thiosulfate were used as electron acceptors by strains ASv26 T , PSv29 T and LSv54 T , and all strains except PSv29 T grew with Fe 3+ (ferric citrate) as electron acceptor. Chemotaxonomy based on cellular fatty acid patterns and menaquinones showed good agreement with the phylogeny based on 16S rRNA sequences. All strains belonged to the subclass of Proteobacteria but had at least 9% evolutionary distance from known sulfate reducers. Due to the phylogenetic and phenotypic differences between the new isolates and their closest relatives, establishment of the new genera Desulfotalea gen. nov., Desulfofaba gen. nov. and Desulfofrigus gen. nov. is proposed, with strain ASv26 T as the type strain of the type species Desulfofrigus oceanense sp. nov., LSv21 T as the type strain of Desulfofrigus fragile sp. nov., PSv29 T as the type strain of the type species Desulfofaba gelida sp. nov., LSv54 T as the type strain of the type species Desulfotalea psychrophila sp. nov. and LSv514 T as the type strain of Desulfotalea arctica sp. nov. Key Words: sulfate-reducing bacteria • psychrophiles • chemotaxonomy • Arctic sediment • Svalbard The GenBank accession numbers for the 16S rDNA sequences of Desulfotalea arctica LSv514 T , Desulfotalea psychrophila LSv54 T , Desulfofaba gelida PSv29 T , Desulfofrigus oceanense ASv26 T and Desulfofrigus fragile LSv21 T are AF099061 -AF099065 , respectively.