Viable and direct bacterial counts from ODP Holes 112-680C and 112-681C (Table 2)

Microbiological examination of sediment cores from the Peru margin (Leg 112) has produced highly significant results: (1) bacteria were present at all sediment depths sampled to 80 meters below seafloor (mbsf); (2) Bacteria were observed in the process of cell division at all but one depth to 80 mbsf; (3) Viable bacteria of different types (heterotrophs, sulfate-reducing, nitrate-reducing, methanogenic, and hydrocarbon oxidizing) have been isolated from many of the sediment samples, including those at 80 mbsf; and (4) Potential activity rates for sulfate reduction and methanogenesis have been determined and are consistent with the distribution of the respective bacteria and in-situ chemical profiles within the sediment. In combination, these results unequivocally demonstrate the presence and activity of bacteria within deep sediment layers.