NHEJ protects mycobacteria in stationary phase against the harmful effects of desiccation.
The physiological role of the non-homologous end-joining (NHEJ) pathway in the repair of DNA double-strand breaks (DSBs) was examined in Mycobacterium smegmatis using DNA repair mutants (DeltarecA, Deltaku, DeltaligD, Deltaku/ligD, DeltarecA/ku/ligD). Wild-type and mutant strains were exposed to a range of doses of ionizing radiation at specific points in their life-cycle. NHEJ-mutant strains (Deltaku, DeltaligD, Deltaku/ligD) were significantly more sensitive to ionizing radiation (IR) during stationary phase than wild-type M. smegmatis. However, there was little difference in IR sensitivity between NHEJ-mutant and wild-type strains in logarithmic phase. Similarly, NHEJ-mutant strains were more sensitive to prolonged desiccation than wild-type M. smegmatis. A DeltarecA mutant strain was more sensitive to desiccation and IR during both stationary and especially in logarithmic phase, compared to wild-type strain, but it was significantly less sensitive to IR than the DeltarecA/ku/ligD triple mutant during stationary phase. These data suggest that NHEJ and homologous recombination are the preferred DSB repair pathways employed by M. smegmatis during stationary and logarithmic phases, respectively.
Pitcher
Robert S
RS
Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RQ, UK.
Green
Andrew J
AJ
Brzostek
Anna
A
Korycka-Machala
Malgorzata
M
Dziadek
Jaroslaw
J
Doherty
Aidan J
AJ
D002470:Cell Survival / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects*; D003890:Desiccation; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000528:radiation effects*; D011839:Radiation, Ionizing; D011995:Recombination, Genetic / Q000528:radiation effects*