Use of 16S rRNA oligonucleotide probes to monitor sulfate-reducing bacteria, archaea and Fe(II) oxidizer in the Okinawa Trough basin

The microbial world of the deep subsurface environment located off the east coast of Taiwan, in the most southern part of the so-called Okinawa Trough , was studied using specific 16S rRNA oligonucleotides to target selected r educing and oxidizing bacteria. The sampling area consists of a cluster of volcanoes under an anoxic sea bottom. Sulfate-reducing bacteria were found to be dominant, by membrane hybridization with an SRB804 probe. Archaea was the second major group and was detected using an ARC915 probe. Very few ni trate-dependent ferrous iron oxidizers were identified in this extremely an oxygenic environment. Since adaptation to a habitat by reducing or oxidizin g bacteria depend upon the redox potential of an environment, the sulfate-r educing bacteria and Archaea found suggest that the collected sediments off er extremely anoxygenic conditions. Results further indicated the absence o f oxygen at the hydrothermal vents of the volcano in the area investigated which shows that the volcano is dormant.