LONGEVITY OF SELECTED EXOGENOUS MICROORGANISMS IN THE RUMEN

Abstract

Various microorganisms commonly believed to be exogenous to the rumen were introduced directly into the rumina of cattle, and the microbial populations that survived were determined. Approximate times required for one decimal reduction in plate count were Chromobacterium violaceum, 2 hours; laboratory strain of Serratia marcescens, 4 hours; Serratia sp. isolated from the rumen, over 8 hours; vegetative cells of Bacillus stearothermophilus, 3 hours; spores of B. stearothermophilus, 4 hours; yeasts (Candida krusei and Hansenula anomala) from high moisture corn, 8 hours; and S. marcescens bacteriophage, over 8 hours. Survival of the test organisms was affected by inoculum size; an increase in the inoculum size resulted in a reduced rate of death. These results suggest that the times required for death of exogenous microorganisms in the rumen are much greater than most ruminologists heretofore thought.When cells susceptible to Serratia sp. phages were inoculated simultaneously with homologous phages into the rumen, the phages apparently attached themselves to the cells and were inactivated. No burst (release of phage) was observed during the experimental period.Chromobacterium violaceum and S. marcescens survived for periods of about 10 times longer when the cells were placed in VIVAR jars (in vivo artificial rumens) than when the cells were inoculated directly into the rumen. These results indicate that data obtained by using VIVAR jars should be interpreted with caution.