Single molecule tracking reveals spatio-temporal dynamics of bacterial DNA repair centres.

Single-particle (molecule) tracking (SPT/SMT) is a powerful method to study dynamic processes in living bacterial cells at high spatial and temporal resolution. We have performed single-molecule imaging of early DNA double-strand break (DSB) repair events during homologous recombination in the model bacterium Bacillus subtilis. Our findings reveal that DNA repair centres arise at all sites on the chromosome and that RecN, RecO and RecJ perform fast, enzyme-like functions during detection and procession of DNA double strand breaks, respectively.

Bacillus subtilis hlpB encodes a conserved stand-alone HNH nuclease-like protein that is essential for viability unless the hlpB deletion is accompanied by the deletion of genes encoding the AddAB DNA repair complex.

The HNH domain is found in many different proteins in all phylogenetic kingdoms and in many cases confers nuclease activity. We have found that the Bacillus subtilis hlpB (yisB) gene encodes a stand-alone HNH domain, homologs of which are present in several bacterial genomes. We show that the protein we term HlpB is essential for viability.