A novel inducible prophage from the mycosphere inhabitant Paraburkholderia terrae BS437

Bacteriophages constitute key gene transfer agents in many bacteria. Specifically, they may confer gene mobility to Paraburkholderia spp. that dwells in soil and the mycosphere. In this study, we first screened mycosphere and bulk soils for phages able to produce plaques, however found these to be below detection. Then, prophage identification methods were applied to the genome sequences of the mycosphere-derived Paraburkholderia terrae strains BS001, BS007, BS110 and BS437, next to P. phytofirmans strains BS455, BIFAS53, J1U5 and PsJN. These analyses revealed all bacterial genomes to contain considerable amounts [up to 13.3%] of prophage-like sequences. One sequence predicted to encode a complete phage was found in the genome of P. terrae BS437. Using the inducing agent mitomycin C, we produced high-titered phage suspensions. These indeed encompassed the progeny of the identified prophage (denoted ɸ437), as evidenced using phage major capsid gene molecular detection. We obtained the full sequence of phage ɸ437, which, remarkably, had undergone a reshuffling of two large gene blocks. One predicted moron gene was found, and it is currently analyzed to understand the extent of its ecological significance for the host.