Polaromonas hydrogenivorans sp. nov., a psychrotolerant hydrogen-oxidizing bacterium from Alaskan soil.

Psychrotolerant (0-25 degrees C), chemolithotrophic Gram-negative cocci were isolated from Alaskan forest soil. The novel isolate was found to grow autotrophically on H(2) : CO(2) mixtures and to switch to heterotrophic growth on media containing organic substrates. The novel strain utilized a wide range of organic acids, some simple sugars and alcohols. Naphthalene vapour did not support growth. On the basis of 16S rRNA gene sequence similarity, the novel strain is affiliated to the genus Polaromonas, of the class Betaproteobacteria, and is related to Polaromonas naphthalenivorans (99.6 % gene sequence similarity), Polaromonas aquatica (97.4 %) and Polaromonas vacuolata (96.1 %). The membrane phospholipids contained 16 : 1omega7c/16 : 1omega6c, 16 : 0 and 18 : 1omega7c, similar to the fatty acids found for P. naphthalenivorans, P. aquatica and P. vacuolata. On the basis of DNA-DNA hybridization, physiological and biochemical properties, the hydrogen-oxidizing mixotrophic isolate represents a novel species, for which the name Polaromonas hydrogenivorans sp. nov. is proposed. The type strain is DSM 17735(T) (=NRRL B-41369(T)).