Thermodesulfovibrio a possible indicator of Hydrothermal fluids

Abstract

Marine bacteria inhabited in the hydrothermal vent area obtain energy by the oxidation of various gases and/or minerals in the vent fluid. Bacterial community structure of the sediments from two different deep sea mountains, TA22 & TA26, on the Tofua Arc in the Southern Pacific Ocean was investigated by the deep sequencing of 16S rRNA gene partial fragments. Community structure at surface area to the depth of 5 cm of TA22 and those in TA26 to the depth of 15 cm at the phylum level was not markedly different but that at deeper than 5 cm in TA26 was quite different. The proportion of sequences affiliated to the phylum OD1, OP3, Nitrospirae, SAR406, and GN04 was higher but frequency of Acidobactria, SAR202, Gemmatimonadetes, and Proteobacteria was lower in the 5 to 10 cm depth at TA26 compared to those in other samples. The community composition of phylum Nitrospirae was investigated further and found that sequences affiliated into the class Thermodesulfovibrio suddenly increased in TA26 with increase of sediment depth but that of class Nitrospira was dominant in the TA22 at all sampled depths. Qualitative estimation of sulfur contents was increased with depth from 3 cm in TA26 and markedly higher than that in TA22. This result implied that frequency of several bacterial phyla or class, especially members affiliated into the class Thermodesulfovibrio reflects the existence of geothermal fluids and, it could be an indicator of hydrothermal vent.