Natural variability and diurnal fluctuation of bacteriophage populations in the rumen

Abstract

The effects of pbages on ruminaJ bacterial populations and consequent effects on nutrition and animal production are poorly understood. By examining phage DNA in rumen fluid it is possible to estimate ruminal bacteriophage numbers by using pulsed field gel electrophoresis and laser densitometry. With this method phage numbers were estimated to be between 3 x 109 and 1.6 x 1010 panicles mr I of rumen fluid. The phage population of the rumen appears to have two major components, a broad region comprising DNA from many phages (presumptively including temperate phages), and discrete bands of DNA from one or a few phage genotypes
(presumptively representing lytic phage blooms). A study to determine the extent of natural fluctuations in ruminal phage populations was undcnaken. Phage DNA banding patterns and total phage DNA mi- 1 of rumen fluid were found to be highly variable between; (a) species of ruminants, (b) animals at pasture and in pens. (c) animals penned together and on the same diet, and (d) the same animal sampled at
the same time of day on consecutive days. When a singl~ animal, fed once daily an oaten chaff-alfalfa (70:30) diet. was sampled at two-hourly intervals the phage population changed only slowly. with no apparent change between some two-hourly intervals. A marked diurnal variation in the phage population (up to ten-fold increase) in total phage DNA mr 1 of RF occurred 6-8 hours after feeding in these animals. This surge in phage activity is currently under examination.
In conclusion, the phage population of the rumen is highly dynamic. The numbers and fluctuations in the phage population suggest that phages may play an important
role in turnover of microbial cells and supply of protein to the animal.