Thioclava electrotropha sp nov., a versatile electrode and sulfur-oxidizing bacterium from marine sediments

A taxonomic and physiologic characterization was carried out on Thioclava strain ElOx9(T), which was isolated from a bacterial consortium enriched on electrodes poised at electron donating potentials. The isolate is Gram-negative, catalase-positive and oxidase-positive; the cells are motile short rods. The bacterium is facultatively anaerobic with the ability to utilize nitrate as an electron acceptor. Autotrophic growth with H-2 and S-0 (oxidized to sulfate) was observed. The isolate also grows heterotrophically with organic acids and sugars. Growth was observed at salinities from 0 to 10% NaCl and at temperatures from 15 to 41 degrees C. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belongs in the genus Thioclava; it had the highest sequence similarity of 98.8% to Thioclava atlantica 13D2W-2(T), followed by Thioclava dalianensis DLFJ1-1(T) with 98.5% similarity, Thioclava pacifica TL 2(T) with 97.7% similarity, and then Thioclava indica DT23-4(T) with 96.9 %. All other sequence similarities were below 97% to characterized strains. The digital DNA-DNA hybridization estimated when compared to T. atlantica 13D2W-2(T), T. dalianensis DLFJ1-1(T), T. pacifica TL 2(T) and T. indica DT23-4(T) were 15.8 +/- 2.1, 16.7+2.1, 14.3 +/- 1.9 and 18.3 +/- 2.1 %. The corresponding average nucleotide identity values between these strains were determined to be 65.1, 67.8, 68.4 and 64.4 %, respectively. The G+C content of the chromosomal DNA is 63.4 mol%. Based on these results, a novel species Thioclava electrotropha sp. nov. is proposed, with the type strain ElOx9(T) (= DSM 103712(T) = ATCC TSD-100(T)).