Isolation of a virulent bacteriophage from a Propionibacterium species in the sheep rumen

Abstract

Propionibacterium is a facultative anaerobe associated with the rumen epithelium, the presence of which may influence the anaerobic environment through oxygen scavenging, as well as providing a source of propionate. Factors such as bacteriophages that influence Propionibacterium populations may therefore be important regulators of rumen function. This study describes the isolation and identification of a ruminal Propionibacterium bacteriophage. Sheep rumen fluid was screened for Propionibacterium species and 3 isolates were identified and characterised. One isolate, PA1, was used as an indicator strain to screen for the presence of Propionibacterium-specific virulent bacteriophages. A virulent bacteriophage, PB2, was isolated from clear plaques on a lawn of PA1 cells and was shown by transmission electron microscopy to be a siphovirus-like particle comprising an icosahedral head 50 nm in diameter and a tail 140 nm in length. The bacteriophage was visibly attached to and within PA1 cells, and was shown to infect all 3 ruminal isolates of Propionibacterium and 4 of 6 clinical isolates of P. acnes. Restriction mapping of bacteriophage PB2 demonstrated a 30.8 kb genome.