This is a draft schedule. Presentation dates, times and locations may be subject to change.
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Identification of Six Uncultured Rumen Bacteria from Different Phylogenetic Lineages Using Cellulose As a Selection Agent
Lee J. Opdahl, Michael G. Gonda, and Benoit St-Pierre
Department of Animal Science, South Dakota State University, Brookings
The microbial-driven process of converting cellulosic biomass into utilizable energy is a defining feature of ruminant animals. Due to the complexity of rumen microbial communities, the vast majority of these rumen microorganisms remain uncharacterized. In order to gain further insight, selection-based batch culturing from bovine rumen fluid was used to identify previously uncharacterized rumen bacteria capable of metabolizing cellulose. Each independent trial consisted of 3 replicate cultures supplemented with cellulose (Sigma, cat# C8002) and 2 replicate cultures with no added substrate. 16S rRNA-based population analysis was used to identify rumen bacteria enriched within 14 days of culturing. A total of 116,111 to 336,246 high quality, non-chimeric sequence reads per trial were used for Operational Taxonomic Unit (OTU) clustering. As a result of 3 trials, seven different candidate cellulose-utilizing species-level OTUs were identified. Six of the enriched OTUs showed increased levels ranging between 140 and 500-fold increases compared to their respective rumen inocula, representing 14.1% to 41.3% of reads in samples supplemented with cellulose. One OTU corresponded to a known species (Ruminococcus flavefaciens), four were predicted to be uncultured species of known genera (Rummellibacillus sp., Ethanoligenens sp., and 2 Prevotella spp.), and one was assigned to the family Ruminococcaceae. The remaining OTU (Prevotella sp.) was found in moderately high abundance in the rumen inoculum (5.8%) and was enriched 2.5-fold (15.6%). While future research is necessary to further characterize their involvement in cellulose metabolism, identification of these bacteria will provide additional insights towards a better understanding of ruminal cellulose metabolism.