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

Abstract

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)).