Hydrogenophilus hirschii sp nov., a novel thermophilic hydrogen-oxidizing beta-proteobacterium isolated from Yellowstone National Park

A novel thermophilic hydrogen-oxidizing bacterium, Hydrogenophilus hirschii YeI5a(T) (= DSM 11420(T) = JCM 10831(T)) has been isolated from the Angel Terrace Spring, Yellowstone National Park. The isolate was rod-shaped (1.0 - 1.5 x 0.8 mum) with a polarly inserted flagellum, cells grew chemolithoau totrophically under an atmosphere of H-2 and CO2 (80:20) in the presence of low concentrations of O-2 (optimum 2.5 %), Organotrophic growth occurred o n complex organic substrates such as yeast extract and peptone and on organ ic acids. Carbohydrates and amino acids were not utilized, The strain grew between 50 and 67 degreesC; optimal growth occurred at a temperature of 63 degreesC. The pH optimum was 6.5, NaCl inhibited growth at concentrations h igher than 1.5%. The major respiratory lipoquinone was ubiquinone-8. Analys is of fatty acids of YeI5a(T) revealed a straight-chain saturated C-16:0 as the major component followed by cycle C-17:0 and cycle C-19:0. The G+C con tent of total DNA was 61 mol%, Phylogenetic analysis placed the strain in t he beta -proteobacteria. The 16S rDNA sequence of strain YeI5a(T) was relat ed to that of Hydrogenophilus thermoluteolus, To our knowledge, Hydrogenoph ilus hirschii is the most thermophilic micro-organism found within the prot eobacteria that grows in the temperature range 50-68 degreesC.