In Vitro Studies of the Effect of Aureomycin and Terramycin on Mixed Suspensions of Bovine Rumen Bacteria

Summary No significant or consistent difference was observed between heated and nonheated suspension of bovine rumen bacteria in their ability to inactivate aureomycin and terramycin. The presence of a specific heat-labile inhibitor such as an aureomycinase could not be demonstrated in either the mixed suspensions of rumen cells or in the rumen fluid itself. A nonspecific type of inactivation was observed in some instances with aureomycin, and this was most probably due to the protein nature of the mixed suspensions of rumen cells. The presence of both aureomycin and terramycin (100 γ per milliliter) definitely decreased the ability of rumen bacteria in the resting state to utilize the carbohydrates xylose, arabinose, glucose, maltose, and cellobiose in vitro. Aureomycin and terramycin when added to a plating medium (final concentration 25 γ per milliliter) completely inhibited the growth of bovine rumen bacteria, whereas when this concentration was added to rumen fluid, then plated, it did not. Suggestions for the direction in which further research on this problem should proceed are presented.