DEVELOPMENT OF AN OLIGONUCLEOTIDE PROBE TARGETING 16S RIBOSOMAL-RNA AND ITS APPLICATION FOR DETECTION AND QUANTITATION OF THE RUMINAL BACTERIUM SYNERGISTES-JONESII IN A MIXED-POPULATION CHEMOSTAT

Radiolabelled and fluorescent-dye-conjugated oligonucleotide probes wh ich targeted rRNA sequences were developed for the enumeration of the ruminal bacterium Synergistes jonesii 78-1 in mixed culture. Two probe s were tested, and both were highly specific for the respective comple mentary sequences of the target organism. Individual cells of S. jones ii in pure and mixed cultures were clearly visualized in situ by hybri dization with the fluorescent-dye-conjugated probe but could not be de tected in natural samples. Therefore the radiolabelled probe was used to monitor the population of S. jonesii introduced into a chemostat wh ich simulated the rumen ecosystem. The S. jonesii probe did not hybrid ize to RNA extracted from the culture prior to inoculation with the ta rget organism. After inoculation, S.jonesii rRNA represented 4.5% of t he total bacterial rRNA and then rapidly declined to <0.2% before incr easing to about 1% of the total bacterial rRNA during the following 3 weeks. This study demonstrates that rRNA-targeted probes could be used for tracking organisms introduced into the rumen ecosystem.