Hydrogenophilus islandicus sp. nov., a thermophilic hydrogen-oxidizing bacterium isolated from an Icelandic hot spring.

A novel chemolithotrophic bacterium, strain 16C(T), was isolated from a hot spring in Graendalur, south-west Iceland. Cells of this organism were Gram-negative, rod-shaped and motile. The isolate was aerobic and capable of chemolithotrophic growth on hydrogen and carbon dioxide, heterotrophic growth on butyrate and several other organic compounds, and mixotrophic growth on butyrate, hydrogen and carbon dioxide. Heterotrophic growth was generally enhanced in the presence of yeast extract. Autotrophic growth on hydrogen was observed at pH values between 6.0 and 10.0 and temperatures between 35 and 60 °C; optimum growth conditions were pH 7.0 and 55 °C. The DNA G+C content was 63.9 mol%. 16S rRNA gene sequence analysis showed that strain 16C(T) was a member of a distinct species belonging to the class Betaproteobacteria and was most closely related to Hydrogenophilus thermoluteolus NBRC 14978(T) and Hydrogenophilus hirschii DSM 11420(T). The major cellular fatty acids were straight-chain C(16 : 0) (44.98 %) and C(18 : 1)ω7c (17.93 %), as well as cyclic C(17 : 0) (13.90 %) and C(19 : 0)ω8c (4.67 %) fatty acids. Based on its physiological and molecular properties, it is concluded that strain 16C(T) represents a novel species within the genus Hydrogenophilus, for which the name Hydrogenophilus islandicus is proposed; the type strain is 16C(T) (=DSM 21442(T)=JCM 16106(T)).

Thiomonas islandica sp. nov., a moderately thermophilic, hydrogen- and sulfur-oxidizing betaproteobacterium isolated from a hot spring.

A novel, hydrogen- and sulfur-oxidizing bacterium, designated strain 6C(T), was isolated from a hot spring in Graendalur, south-western Iceland. Cells of this organism were Gram-reaction-negative, rod-shaped and motile. The strain grew aerobically and was capable of chemolithotrophic growth on thiosulfate and hydrogen, heterotrophic growth on pyruvate, oxalate, acetate and on glutamate in the presence of yeast extract and mixotrophic growth on several organic compounds, thiosulfate and/or hydrogen. During growth on thiosulfate, the final product was sulfate, resulting in a drop in pH from 6.8 to 2.7. Heterotrophic growth on pyruvate was observed at pH 4-7 (optimum pH 4) and 35-50 °C (optimum 45 °C). The DNA G+C content was 65.2 mol%. As determined by 16S rRNA gene sequence analysis, strain 6C(T) represents a distinct species belonging to the class Betaproteobacteria and is most closely related to Thiomonas intermedia DSM 18155(T) and Thiomonas perometabolis DSM 18570(T). DNA-DNA hybridization between strain 6C(T) and Thiomonas intermedia DSM 18155(T) and Thiomonas perometabolis DSM 18570(T) gave relatedness values below 32 %. These results, together with physiological characteristics, showed that strain 6C(T) represents a novel species within the genus Thiomonas, for which the name Thiomonas islandica sp. nov. is proposed. The type strain is 6C(T) (=DSM 21436(T) =JCM 16107(T)).