ARS | Publication request: COMPETITION AMONG RUMINAL CELLULOLYTIC BACTERIA FOR CELLULOSE IN DEFINED COCULTURE

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 23, 1996
Publication Date: N/A

Technical Abstract: Three predominant ruminal cellulolytic species (Fibrobacter succinogenes S85, Ruminococcus flavefaciens FD-1, and Ruminococcus albus 7) were grown in different binary combinations to examine the outcome of competition in cellulose-excess batch culture or in cellulose-limited continuous culture. Relative populations of each species were estimated using signature membrane fatty acids and 16S rRNA-targeted oligonucleotide probes. Both S8 and FD-1 coexisted in cellulose-excess batch culture with similar population sizes. By contrast, under cellulose limitation FD-1 predominated (> 95% of total cell mass) in coculture with S85, probably because of FD- 1's greater adherence to cellulose and higher affinity for cellodextrin products of cellulose hydrolysis. Batch cocultures of S85 and 7 contained similar (p<.05) populations of the two species. However, under cellulose limitation, S85 predominated (79% of cell mass) in cultures simultaneously coinoculated with 7. Results from batch cocultures of FD-1 and 7 were not consistent within or among trials: some experiments yielded monocultures of 7 (suggesting production of an inhibitory agent by 7), while others contained substantial populations of both species. Under cellulose limitation, FD-1 predominated over 7 (85% and 15%, respectively), as would be expected by greater adherence to cellulose by FD-1. The retention of 7 in the cellulose-limited coculture may result from a combination of its ability to utilize glucose (which is not utilizable by FD-1); its demonstrated ability to adapt under selective pressure in continuous culture to utilization of lower concentrations of cellobiose, a major product of cellulose hydrolysis; and its possible production of an inhibitory agent.