Nonhomologous end joining in bacteria

DNA can be so severely damaged that both strands of the duplex are broken to produce double-strand breaks (DSBs). Bacterial cells, like mammalian cells, can survive this potentially lethal form of damage by using specialized repair proteins to mend the breaks. Ku proteins bind to the ends of broken DNA and recruit a specific DNA repair ligase (LigD) to the break sites. Bacterial LigD is a multifunctional enzyme complex that can rejoin DSBs, even if both strands do not accurately match. This process is known as nonhomologous end joining (NHEJ). LigD is highly versatile and can repair blunt ends, as well as breaks, with mismatching single-stranded DNA termini. NHEJ is not as accurate as homologous recombination, a distinct DSB repair pathway that uses a second homologous copy of DNA as a template to recreate lost genetic material. NHEJ is the primary pathway for DSB repair in the stationary phase of the cell cycle when no homologous template is available.