A COMBINED ECOLOGICAL AND PHYSIOLOGICAL APPROACH TO STUDYING SULFATE REDUCTION WITHIN DEEP MARINE SEDIMENT LAYERS

Details of techniques and approaches for a comprehensive and integrated study of bacteria in deep marine sediment layers are presented. The effectiveness of these techniques is documented by reference to anaerobic sulphate-reducing bacteria and their associated activity in deep sediments from the Japan Sea and Peru Margin. The effect of sample storage and pressure on the results obtained is considered. The characteristics of enrichment cultures of sulphate-reducing bacteria demonstrate that they are metabolically diverse, and that this diversity is maintained with increasing sediment depth. Pure cultures of sulphate-reducing bacteria from 80 and 500 m are barophilic. Maximum growth occurs at their calculated in situ pressure, which demonstrates their deep sea origin. These and other data [1-6] demonstrate the presence of a deep bacterial biosphere (to a depth of at least 500 m) within marine sediments, which is well adapted to this extreme environment. These techniques should be applicable to other subsurface environments where a combination of low bacterial populations and activities provide a major challenge to the study of microbial ecology.