The genetics of rumen phage populations

Abstract

The microbial populations of the rumen are widely recognised as being essential for ruminant nutrition and health, utilising and breaking down fibrous plant material which would otherwise be indigestible. The dense and highly diverse viral populations which co-exist with these microbial populations are less understood, despite their potential impacts on microbial lysis and gene transfer. In recent years, studies using metagenomics, metatranscriptomics and proteomics have provided new insights into the types of viruses present in the rumen and the proteins they produce. These studies however are limited in their capacity to fully identify and classify the viral sequence information obtained, due to the absence of rumen-specific virus genomes in current sequence databases. The majority of commensal viruses found in the rumen are those infecting bacteria (phages), therefore we genome sequenced phage isolates from our phage culture collection infecting the common rumen microbial genera Bacteroides, Ruminococcus and Streptococcus. We also created a pan-genome using 39 whole genome sequences of predominantly livestock-derived Streptococcus isolates (representing S. bovis, S. equinus, S. henryi, and S. gallolyticus), to identify and characterise integrated viral genomes (prophage sequences). Collectively this approach has provided novel rumen phage sequences to increase the accuracy of rumen metagenomics analyses. It has also provided new insights into how viruses or virus-encoded proteins can potentially be used to modulate specific microbial populations within the rumen microbiome.