Thirteen novel, obligately anaerobic, thermoacidophilic bacteria were isolated from deep-sea hydrothermal vent sites. Four of the strains, designated EP5-rT, KM1, Mar08-272rT and Mar08-368r, were selected for metabolic and physiological characterization. With the exception of strain EP5-rT, all strains were short rods that grew between 40 and 72 °C, with optimal growth at 60-65 °C. Strain EP5-rT was more ovoid in shape and grew between 45 and 75 °C, with optimum growth at 60 °C. The pH range for growth of all the isolates was between pH 3.5 and 5.5 (optimum pH 4.5 to 5.0). Strain Mar08-272rT could only grow up to pH 5.0. Elemental sulfur was required for heterotrophic growth on acetate, succinate, Casamino acids and yeast extract. Strains EP5-rT, Mar08-272rT and Mar08-368r could also use fumarate, while strains EP5-rT, KM1 and Mar08-272rT could also use propionate. All isolates were able to grow chemolithotrophically on H2, CO2, sulfur and vitamins. Phylogenetic analysis of 16S rRNA gene sequences placed all isolates within the family Desulfurellaceae of the class Deltaproteobacteria, with the closest cultured relative being Hippea maritima MH2T (~95-98 % gene sequence similarity). Phylogenetic analysis also identified several isolates with at least one intervening sequence within the 16S rRNA gene. The genomic DNA G+C contents of strains EP5-rT, KM1, Mar08-272rT and Mar08-368r were 37.1, 42.0, 35.6 and 37.9 mol%, respectively. The new isolates differed most significantly from H. maritima MH2T in their phylogenetic placement and in that they were obligate thermoacidophiles. Based on these phylogenetic and phenotypic properties, the following two novel species are proposed: Hippea jasoniae sp. nov. (type strain Mar08-272rT = DSM 24585T = OCM 985T) and Hippea alviniae sp. nov. (type strain EP5-rT = DSM 24586T = OCM 986T).
|Original language||English (US)|
|Number of pages||7|
|Journal||International Journal of Systematic and Evolutionary Microbiology|
|State||Published - Jun 2012|