Persephonella marina gen. nov., sp. nov. and Persephonella guaymasensis sp. nov., two novel, thermophilic, hydrogen-oxidizing microaerophiles from deep-sea hydrothermal vents

D. Gotz, A. Banta, T. J. Beveridge, A. I. Rushdi, BRT. Simoneit and A. L. Reysenbach Department of Biology, Portland State University, Portland, OR 97201, USA Two thermophilic, strictly chemolithoautotrophic, microaerophilic, hydrogen-oxidizing members of the Bacteria designated strain EX-H1(T) and strain EX-H2(T) were isolated from two separate deep-sea hydrothermal vent sites at 9degrees N 104degrees W in the Pacific Ocean and Guaymas Basin. The motile 2--4-microm-long rods were Gram-negative and non-sporulating. The temperature range for growth was between 55 and 80 degrees C for EX- H1(T) (optimum at 73 degrees C) and 55--75 degrees C for EX-H2(T) (optimum at 70 degrees C). Both strains grew fastest at 2.5% (w/v) NaCl and at pH 6, although growth was observed from pH 4.7 to pH 7.5. EX-H1(T) and EX-H2(T) were able to use elemental sulfur, thiosulfate or hydrogen as an electron donor, and oxygen (2--3%, v/v) or nitrate as an electron acceptor. EX-H1(T) was also able to use elemental sulfur as an electron acceptor. EX-H1(T) and EX-H2(T) further differed in their genomic G+C content (38.5 and 37.4 mol%, respectively) and 16S rRNA sequences (4% difference). Maximum-likelihood analysis of the 16S rRNA phylogeny placed both isolates within the Aquificales as a distinct lineage and showed them to be only about 85% similar to Aquifex pyrophilus. On the basis of phenotypic and phylogenetic characteristics, it is proposed that EX-H1(T) and EX-H2(T) belong to a new genus within the Aquificales, namely Persephonella gen. nov. It is further proposed that EX-H1(T) be named Persephonella marina sp. nov., the type species of the genus, and that EX-H2(T) be named Persephonella guaymasensis sp. nov., a second species in this genus.