Marinobacter santoriniensis sp. nov., an arsenate-respiring and arsenite-oxidizing bacterium isolated from hydrothermal sediment.

A Gram-negative, arsenate-respiring and arsenite-oxidizing marine bacterium, NKSG1(T), was isolated from hydrothermal sediment at Santorini, Greece. Strain NKSG1(T) was a facultatively anaerobic, motile, non-spore-forming, rod-shaped bacterium. Growth occurred optimally at 35-40 degrees C, between pH 5.5 and 9.0 and with 0.5-16 % NaCl. Energy was conserved by the aerobic oxidation of a range of complex substrates, carbohydrates and organic acids, or anaerobically by arsenate reduction, nitrate reduction coupled to the oxidation of organic carbon or lactate fermentation. Oxidation of arsenite and anaerobic nitrate-dependent oxidation of Fe(II) were facilitated by the presence of an organic carbon source. The DNA G+C content was 58.1 mol%. The major respiratory quinone was Q-9. The significant fatty acids were 16 : 1omega9c, summed feature 3 (iso-15 : 0 2-OH/16 : 1omega7c), 16 : 0 and 18 : 1omega9c. Analysis of 16S rRNA gene sequences showed that strain NKSG1(T) fits within the phylogenetic cluster of the genus Marinobacter and is most closely related to Marinobacter koreensis DD-M3(T) (99.3 % similarity). The degree of relatedness with M. koreensis DSM 17924(T) based on DNA-DNA hybridization was 56 %. The results of a polyphasic study indicated that strain NKSG1(T) is a representative of a novel species within the genus Marinobacter, for which the name Marinobacter santoriniensis sp. nov. is proposed. The type strain is NKSG1(T) (=DSM 21262(T) =NCIMB 14441(T)=ATCC BAA-1649(T)). The capacity for arsenic reduction or oxidation has not been demonstrated previously for this genus.