Changes in the microbial community in Japan Trench sediment from a depth of 6292 m during cultivation without decompression

A sample of deep-sea sediment was obtained from the Japan Trench at a depth of 6292 m using a pressure-retaining sediment sampler. Microorganisms in t he sediment sample were cultivated in marine broth 2216 at ambient pressure (65 MPa) without decompression, and at atmospheric pressure (0.1 MPa) as a control experiment. 16S ribosomal RNA genes (rDNA) were amplified by PCR f rom DNA extracted from the original sediment sample and the mixed cultures, and the nucleotide sequences were determined. The results of phylogenetic analysis based on 16S rDNA sequences indicated that microbial diversity in the original sediment samples showed a wide distribution of types in the do main Bacteria. Furthermore, in the mixed cultures incubated at 65 MPa witho ut decompression, bacterial strains belonging to the Shewanella barophiles branch and the genus Moritella existed together at the beginning of cultiva tion, and Moritella strains became dominant towards the end of the cultivat ion period. Finally, in the mixed cultures incubated at atmospheric pressur e, strains belonging to the genus Pseudomonas were dominant at all times. A nalysis of fatty acids extracted From the cultures supported the phylogenet ic results. (C) 1999 Federation of European Microbiological Societies. Publ ished by Elsevier Science B.V. All rights reserved.