International Journal of Systematic and Evolutionary Microbiology (2002), 52, 1299–1304 DOI : 10.1099/ijs.0.02139-0 Nautilia lithotrophica gen. nov., sp. nov., a thermophilic sulfur-reducing ε-proteobacterium isolated from a deep-sea hydrothermal vent 1 Institute of Microbiology, Russian Academy of Sciences, Prospect 60-letiya Oktyabrya 7/2, 117811 Moscow, Russia 2 UMR 6539, Centre National de la Recherche Scientifique et Universite ! de Bretagne Occidentale, Institut Universitaire Europe ! en de la Mer, 29280 Plouzane ! , France 3 DSMZ – German Collection of Microorganisms and Cell Cultures, Mascheroder Weg 1b, 38124 Braunschweig, Germany M. L. Miroshnichenko, 1 N. A. Kostrikina, 1 S. L’Haridon, 2 C. Jeanthon, 2 H. Hippe, 3 E. Stackebrandt 3 and E. A. Bonch-Osmolovskaya 1 Author for correspondence : M. L. Miroshnichenko. Tel : ›7 095 135 44 58. Fax: ›7 095 135 65 30. e-mail : mir!inmi.host.ru A novel, strictly anaerobic, thermophilic sulfur-reducing bacterium, strain 525 T , was isolated from tubes of the deep-sea hydrothermal vent polychaete Alvinella pompejana, collected on the East Pacific Rise (13S N). This organism grew in the temperature range 37–68 SC, the optimum being 53 SC, and in the pH range 6<4–7<4, the optimum being 6<8–7<0. The NaCl range for growth was 0<8–5<0 %, the optimum being 3<0 %. Strain 525 T grew lithoautotrophically with H 2 as energy source, S 0 as electron acceptor and CO 2 as carbon source. Alternatively, strain 525 T was able to use formate as an energy source. The GMC content of the genomic DNA was 34<7 mol %. Phylogenetic analysis of the 16S rDNA gene sequence placed strain 525 T in the ε-subclass of the Proteobacteria, where it forms a deep cluster with recently isolated relatives. On the basis of phenotypic and phylogenetic differences between strain 525 T and its closest phylogenetic relatives, it is proposed that the new isolate should be described as a member of a new genus, Nautilia, for which the name Nautilia lithotrophica gen. nov., sp. nov. is proposed. The type strain is strain 525 T (fl DSM 13520 T ). Keywords : deep-sea hot vents, sulfur reduction, thermophile, lithotroph, epsilon- Proteobacteria INTRODUCTION Deep-sea hydrothermal vents represent a unique mi- crobial habitat characterized by extreme temperature gradients and high concentrations of hydrogen sulfide, gases and toxic heavy metals. The vents are colonized by highly specific invertebrate fauna, the growth of which is supported by symbiotic and non-symbiotic chemosynthetic micro-organisms (Jannasch & Mottle, 1985). Alvinella pompejana is a tube-dwelling annelid poly- chaete endemic to the East Pacific Rise ; it inhabits the hot areas of active deep-sea hydrothermal vent chimneys. One of the most striking features of this worm is its obligate association with a highly diverse and dense assemblage of epibiotic micro-organisms. Dorsal epidermal expansions are covered by fila- ................................................................................................................................................. Published online ahead of print on 18 February 2002 as DOI 10.1099/ijs.0.02139-0. The GenBank accession number for the 16S rDNA sequence of strain 525 T is AJ404370. mentous morphotypes that dominate the worm– bacteria association. To date, these dominant morpho- types have eluded all attempts at culture. However, molecular methods have identified constant features of the associated microflora as being those of represent- atives of the ε-subclass of the Proteobacteria (Haddad et al., 1995; Cary et al., 1997). Very recently, four thermophilic ε-Proteobacteria associated with the worm’s epidermis, but phylogenetically distant from its epibionts, were isolated and characterized (Camp- bell et al., 2001). In this study, we report the isolation, from tube fragments of A. pompejana, of a closely related organism and propose that it represents the type species of a new genus. METHODS Sampling. The new strain was isolated from tube fragments of an A. pompejana specimen sampled at the 13 N hy- drothermal vent field (12 48« N, 103 56« W), during the Amistad cruise (in 1999), on the East Pacific Rise at a depth of 2600 m. Enrichment and isolation. For the enrichment of thermo- 02139 # 2002 IUMS Printed in Great Britain 1299