Genomic Survey Reveals no Detectable Bacteriophage Activity in Mycobacterium bovis Across a Large Population.

Abstract

Phages are major drivers of bacterial evolution, yet their ecological and evolutionary interactions with Mycobacterium bovis, a key member of the Mycobacterium tuberculosis complex (MTBC), remain understudied. In this work, we investigate the elusive phage-bacterium interface in M. bovis by integrating comparative genomics of 200 isolates from infected animals with molecular analyses of M. bovis-positive environmental samples. Despite employing diverse and complementary approaches, we found no evidence of active or recent phage infections: no novel prophages beyond the conserved phiRv1, no expansion of CRISPR arrays, and no co-occurrence of M. bovis and mycobacteriophages in host tissues or environmental matrices. Intriguingly, we identified multiple independent excision events of phiRv1 across closely related lineages, suggesting recent prophage mobilization driven by unidentified ecological or genomic triggers. These findings echo previous observations in M. tuberculosis and point toward a stable, phage-scarce landscape across MTBC members. Our results raise compelling questions about the barriers to phage predation in M. bovis, the functionality of its CRISPR-Cas system, and the selective pressures underlying prophage retention and loss. By shedding light on these underexplored dynamics, our study reveals critical gaps in the ecological understanding of M. bovis and highlights opportunities for phage-based innovation in TB control.