Characteristics of saponin-utilizing bacteria from the rumen of cattle.

Evidence for the microbial degradation of plant saponins is limited to few investigations. Rothrock et al. (1955) have reported that the saponins from Dioscorea tubers can be cleaved into their component parts, diosgenin and the sugar moiety, by Aspergillus terreus. Among the bacteria, yeast, and molds examined, only strains of Penicillium, Aspergillus, and Fusarium were capable of hydrolyzing the Dioscorea saponin. Rubin et al. (1953) have isolated unidentified bacteria which grew in a medium with Dioscorea composita saponin as the sole source of carbon. Procedures for the isolation of legume saponins have been developed by Thompson et al. (1957) and these investigators have shown alfalfa saponins are plant glycosides with a triterpenoid sapogenin nucleus and a carbohydrate component. Bloat symptoms have been produced in sheep by the oral and intravenous administration of water soluble alfalfa saponins (Lindahl et al., 1957). Thus the possible relationship of bacterial degradation of legume saponins to bloat assumes particular interest. The proposal has been advanced that, in bloat, ruminal microorganisms might be responsible for an excess production of polysaccharide slime when cattle are on lush pastures such as clover and alfalfa (Hungate et al., 1955), and when animals are maintained on feed-lot rations containing a high percentage of carbohydrate (Jacobson and Lindahl, 1955). The slime contributes to a stable froth formation in which the rumen fermentation gases are retained as numerous small gas bubbles in the ingesta. Changes in the ruminal microbial populations have been shown to occur with the onset of feed-lot bloat symptoms (Gutierrez et al., 1959). This investigation has been directed at the isolation and the characteristics of rumen bacteria capable of degrading alfalfa saponins. A preliminary part of our findings has been published (Gutierrez et al., 1958).