Bacteriophages that infect the cellulolytic ruminal bacterium Ruminococcus albus AR67

Aim: To isolate bacterial viruses that infect the ruminal cellulolytic bacterium Ruminococcus albus. Methods: Four phages infecting R. albus AR67 were isolated under anaerobic conditions using the soft-agar overlay technique. The phages were characterized on morphology, solvent stability, nucleic acid type and digestion characteristics. Two phages, Ra02 and Ra04 comprised icosahedral virions with linear double-stranded DNA and appeared to belong to the family Tectiviridae. The other two phages are most likely filamentous phages with circular single-stranded DNA of the family Inoviridae. Significance of the Study: Viruses of the families Tectiviridae and Inoviridae have not previously been isolated from rumen bacteria. The phages isolated in this study are the first phages shown to infect the cellulolytic bacteria of the rumen. This suggests that the cellulolytic populations of the rumen are subject to lytic events that may impact on the ability of these bacteria to degrade plant fibre and on the nutrition of the animal.