Regulated DNA rearrangement during sporulation in Bacillus weihenstephanensis KBAB4.

Temperate phages can integrate their genomes into a specific region of a host chromosome to produce lysogens (prophage). During genome insertion, prophages may interrupt the gene coding sequence. In Bacillus subtilis, the sigma factor gene sigK is interrupted by a 48 kb prophage-like element. sigK is a composite coding sequence from two partial genes during sporulation. For over two decades, however, no further examples of DNA element-mediated gene reconstitution other than sigK have been identified in spore formers. Here we report that the gene for dipicolinic acid (DPA) synthetase β subunit spoVFB in B. weihenstephanensis KBAB4 is interrupted by a prophage-like element named vfbin. DPA is synthesized in the mother cell and required for maintaining spore dormancy. We found that spoVFB was a composite coding sequence generated in the mother cell via chromosomal rearrangement that excised vfbin. Furthermore, vfbin caused excision after phage-inducer treatment, but vfbin appeared to be defective as a prophage. We also found various spore-forming bacteria in which sporulation-related genes were disrupted by prophage-like DNA elements. These results demonstrate the first example of a similar mechanism that affects a sporulation gene other than sigK and suggest that this prophage-mediated DNA rearrangement is a common phenomenon in spore-forming bacteria.