Abstract
A mesophilic, aerobic, facultatively chemolithoautotrophic bacterium, designated strain EPR70
T
, was isolated from hydrothermal fluids from diffuse-flow vents on the East Pacific Rise at ° 50′ N 10 ° 17′ W. Cells were Gram-negative rods, approximately 0.8–1.0 μm long and 0.3–0.5 μm wide. Strain EPR70
T
grew at 20–40 °C (optimum 30–35 °C), 1–25 % NaCl (optimum 2.5 %) and pH 5.0–7.5 (optimum pH 5.5). The shortest generation time observed for strain EPR70
T
was 42 min. Growth occurred under aerobic chemolithoautotrophic conditions in the presence of thiosulfate and CO
2
. Strain EPR70
T
grew heterotrophically with acetate or n-alkanes as sole carbon and energy sources, and in complex artificial seawater medium. Nitrate was not used as an electron acceptor. The G+C content of the genomic DNA was 64 mol%. Phylogenetic analysis of the 16S rRNA gene indicated that this organism is a member of the class
Gammaproteobacteria
, with
Salinisphaera shabanensis
E1L3A
T
as its closest relative (94 % sequence similarity). On the basis of phylogenetic analyses based on 16S rRNA,
rbcL
and
alkB
genes and physiological analysis, it is proposed that the organism represents a novel species within the genus
Salinisphaera
, for which the name
Salinisphaera hydrothermalis
sp. nov. is proposed. The type strain is EPR70
T
(=DSM 21483
T
=JCM 15514
T
).