ARS | Publication request: PHYLOGENETICALLY-BASED PROBES FOR THE STUDY OF RUMEN MICROBIAL POPULATIONS

Submitted to: Conference on Rumen Function
Publication Type: Abstract Only
Publication Acceptance Date: November 16, 1995
Publication Date: N/A

Technical Abstract: The microbial community structure of model rumen systems (Hoover/Stern) was evaluated using phylogenetically-based probes. The model systems were operated on two separate occasions for 240 h and sampled periodically for nucleic acid extraction and hybridization with radiolabelled oligonucleotide probes complementary to small-subunit (SSU) ribosomal rRNA. Bacterial, eucaryotic and archaeal rRNAs accounted for 32.6% +/- 6.3, 39.5% +/- 6.3, 3.2% +/- 1.1 respectively after 240 h of fermenter operation. Within the archaea, Methanobacteriales accounted for the greatest proportion of the total, 43.5% +/- 1.5 in the inoculum and 28.7% +/- 4.1 after 240 h of operation. We hypothesize that this reduction in Methanobacteriales is a consequence of the loss of protozoa from the systems, as indicated by the reduction in eucaryotic signal. Additional probes were developed for Ruminococcus albus, R. flavefaciens and R. bromii, based upon new and existing gene sequences. R. albus and R. flavefaciens accounted for 1.5% +/- 0.2 and 1.9 +/- 0.2% respectively in the inoculum, and 1.2% +/- 0.3 and 1.9% +/- 0.4 after 168 h of fermenter operation. Cloning and sequencing SSU rRNA genes from total rumen DNA revealed novel Ruminococcus like isolates. These results clearly demonstrate that phylogenetically based probes offer a powerful means of studying both specific microbial populations and the overall community structure of rumen microorganisms. The fermenters appeared to maintain the same bacterial diversity as the rumen derived inoculum.