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 H2 and S⁰ (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 °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).