STUDIES ON RUMEN COLIFORM ORGANISMS: I. INCIDENCE, ISOLATION AND CHARACTERISTICS

Abstract

Bacterial counts on the rumen fluid of two cows fed alfalfa hay revealed the presence of coliform organisms in a concentration in excess of 2% of the total microbial population. When grain was included in the ration of one of the cows, the viable coliform count was of the order of 2.3 × 109 per ml as compared to a maximum of 4 × 108 per ml when hay alone was fed. However, total microscopic counts were also higher when grain was fed, so that the ratio of viable coliform counts to total microscopic counts was not changed. Diurnal variations were observed in viable coliform counts; the numbers increased immediately after feeding and fell off gradually to the prefeeding level after 10 hours. A culture of a coliform organism was isolated from a 10−8 dilution of rumen fluid from a cow fed alfalfa hay. Based on morphological, cultural, physiological and biochemical characteristics, the organism was identified as Escherichia coli type I, and designated E. coli 64. Under aerobic conditions, E. coli 64 entered the exponential phase of growth after 4 hours of incubation with glucose or lactate as substrates and after 5–6 hours when incubated with acetate or glycollate. Under anaerobic conditions, slow growth occurred when the organism was incubated with glucose or lactate, but no growth was observed with acetate or glycollate as substrates.