Pure and Mixed Continuous Culture of Two Rumen Anaerobes

Abstract

This project was designed to determine if Bacteroides ruminicola, while growing in a continuous culture, would liberate sufficient amino acids to sustain the simultaneous growth of a rumen organism which required an amino acid. Initially pure cultures of Bacteroides ruminicola, grown on cellobiose-casein media, solubilized the casein in the media while utilizing peptides and possibly ammonia as nitrogen sources. Pure cultures of Ruminococcus flavefaciens would only grow on the same medium if methionine was added, indicating a requirement for this amino acid. Methionine was not required as the major nitrogen source for Ruminococcus flavefaciens since large amounts of ammonia disappeared from the media during growth. Both organisms were then added to the same culture vessel with a cellobiose-casein medium without free methionine. Bacteroides ruminicola, the faster growing organism, predominated throughout the culture period. After 96 hr, however, Ruminococcus flavefaciens accounted for 20 to 40% of the total bacterial count, indicating Bacteroides ruminicola liberated sufficient methionine to support the growth of Ruminococcus flavefaciens. © 1971, American Dairy Science Association. All rights reserved.