In this study we have incubated samples of deep-ocean water (3170 m) from the Rockall Trough area (North-EastAtlantic)at in-situ temperature (4 1C) andatatmosphericand in-situ pressure (31MPa),and in the absence and presence of added nutrients and observed the Bacterial community structure before and after incubation by means of a nucleic acid based technique (DGGE: Muyzer et al., 1993).