Mycobacterium smegmatis relies on DNA repair pathways to resist DNA damage. Double-strand breaks are especially threatening to bacterial viability. M. smegmatis has three options for repairing double-strand breaks; homologous recombination (HR), non-homologous end joining (NHEJ), and single-strand annealing (SSA). The HR pathway of M. smegmatis is the major determinant of resistance to ionizing radiation and oxidative DNA damage. This pathway involves exchange of information between a damaged chromosome and another homologous chromosome in the same cell. It depends on the RecA protein that catalyzes strand exchange and the ADN protein that acts as a presynaptic nuclease. HR is an accurate repair process and is the preferred pathway during logarithmic growth.
