Nutritional interdependence among rumen bacteria during cellulose digestion in vitro.

A study has been made of the promoting effect of starch on cellulose digestion by mixed rumen bacteria in a cellulose-urea medium. Starch supplementation of the medium promoted the growth of bacteria that required neither amino acids (AA) nor branched-chain fatty acids (BrFA). The growth of these bacteria was followed by the growth of AA-dependent bacteria, AA- or BrFA-dependent bacteria, BrFA-producing bacteria, and finally, BrFA-dependent cellulolytic bacteria. Population changes of these bacterial groups corresponded with a cross-feeding of AA and BrFA and the overall disappearance of cellulose. The data suggest that the nutritional interdependence among rumen bacteria affects the rate of cellulose digestion.