DISTRIBUTION OF MICROORGANISMS IN DEEP-SEA HYDROTHERMAL VENT CHIMNEYSINVESTIGATED BY WHOLE-CELL HYBRIDIZATION AND ENRICHMENT CULTURE OF THERMOPHILIC SUBPOPULATIONS

The microbial community structure of hydrothermal vent chimneys was ev aluated by the combined use of enrichment cultures and whole-cell hybr idizations with fluorescently labeled 16S rRNA-based oligonucleotide p robes, Chimneys were collected during the Microsmoke cruise on the Mid -Atlantic Ridge and were subsampled on board and stored under reduced conditions or fixed. For estimation of culturable thermophiles, select ive media were inoculated by dilution series of the samples and incuba ted at 65, 80, and 95 degrees C, To analyze the microbial diversity of the samples, cells were extracted from the fixed chimney structure sa mples and hybridized with domain- and kingdom-specific probes, Quantif ication of the extracted cells was assessed by whole-cell hybridizatio n on membrane filters, By both methods, the largest amounts of microor ganisms were found in the upper and outer parts of the chimneys, altho ugh even the inner parts contained culturable and detectable amounts o f cells, Different morphotypes of thermophilic and hyperthermophilic m icroorganisms were enriched and detected in samples, Our data clearly indicate that the morphological diversity observed by using whole-cell hybridization is much larger than that assessed by use of culture-bas ed enrichments. This new approach, including culture-independent and - dependent methods to study hydrothermal vent chimneys, showed an uneve n distribution of a diverse microbial community, Application of lower- level specific probes for known families and genera within each domain by our approach, will be useful to reveal the real extent and nature of the chimney microbial diversity and to support cultivation attempts .