Double strand break repair triggers genome plasticity in Streptomyces

Double strand breaks (DSB) are the most detrimental damage that bacterial cells have to cope with. Two main DSB repair pathways, namely homologous recombination (HR) and non-homologous end joining (NHEJ) are in charge of DSB repair. HR relies on an intact copy of the damaged DNA molecule as a template. On the other hand, NHEJ, which is presumably present in only 20% to 25% of the bacteria, is considered as a mutagenic pathway. Hence, in the absence of template, NHEJ is an error-prone mechanism triggering nucleotide additions or deletions at DSB healing site. We recently identified a putative NHEJ repair mechanism in Streptomyces ambofaciens. Among the NHEJ-like genes, we distinguished a set of genes conserved across the Streptomyces species, and a set of variable genes likely inherited by horizontal transfer. Strikingly, both gene sets were involved in response to DNA damage treatments [1].