GROUP-SPECIFIC 16S RIBOSOMAL-RNA-TARGETED OLIGONUCLEOTIDE PROBES TO IDENTIFY THERMOPHILIC BACTERIA IN MARINE HYDROTHERMAL VENTS

Four 16S rRNA-targeted oligonucleotide probes were designed for the de tection of thermophilic members of the domain Bacteria known to thrive in marine hydrothermal systems, We developed and characterized probes encompassing most of the thermophilic members of the genus Bacillus, most species of the genus Thermus, the genera Thermotoga and Thermosip ho, and the Aquificales order, The temperature of dissociation of each probe was determined, Probe specificities to the target groups were d emonstrated by whole-cell and dot blot hybridization against a collect ion of target and nontarget rRNAs, Whole-cell hybridizations with the specific probes were performed on cells extracted from hydrothermal ve nt chimneys, One of the samples contained cells that hybridized to the probe specific to genera Thermotoga and Thermosipho, No positive sign als could be detected in the samples tested with the probes whose spec ificities encompassed either the genus Thermus or the thermophilic mem bers of the genus Bacillus. However, when simultaneous hybridizations with the probe specific to the order Aquificales and a probe specific to the domain Bacteria (R. I. Amann, B, Binder, R, J. Olson, S. W, Chi sholm, R. Devereux, and D, A. Stahl, Appl. Environ, Microbiol, 56:1919 -1925, 1990) were performed on cells extracted from the top and exteri or subsamples of chimneys, positive signals were obtained from morphol ogically diverse bacteria representing about 40% of the bacterial popu lation. Since specificity studies also revealed that the bacterial pro be did not hybridize with the members of the order Aquificales, the de tected cells may therefore correspond to a new type of bacteria, One o f the observed morphotypes was similar to that of a strictly anaerobic autotrophic sulfur-reducing strain that we isolated from the chimney samples, This work demonstrates that application of whole-cell hybridi zation with probes specific for different phylogenetic levels is a use ful tool for detailed studies of hydrothermal vent microbial ecology.