SignificanceAntibiotic resistance leads to substantial mortality and morbidity and significant economic cost because it seriously undermines our ability to treat bacterial infections. Therefore, a better understanding of the effect of antibiotics on bacteria is needed to increase the effectiveness of treatments and slow the emergence of resistance. The bactericidal effects of antibiotics are triggered by target-specific interactions, but there is growing evidence that an important part of their cytotoxicity results from metabolic disturbances induced by treatment. In this article, we report that the perturbation of DNA replication by a wide-spectrum antibiotic, trimethoprim, affects bacterial metabolism, which provokes the production of genotoxic agents and DNA damage, whose processing ultimately contributes to cell death under both aerobic and anaerobic conditions.

SummaryThe sliding clamp proliferating cell nuclear antigen (PCNA) plays a vital role in a number of DNA repair pathways in eukaryotes and archaea by acting as a stable platform onto which other essential protein factors assemble. Many of these proteins interact with PCNA via a short peptide sequence known as a PIP (PCNA interacting protein) motif. Here we describe the identification and functional analysis of a novel PCNA interacting protein NreA that is conserved in the archaea and that has a PIP motif at its C-terminus. Using the genetically tractable euryarchaeon Haloferax volcanii as a model system, we show that the NreA protein is not required for cell viability but that loss of NreA (or replacement of the wild-type protein with a truncated version lacking the C-terminal PIP motif) results in an increased sensitivity to the DNA damaging agent mitomycin C (MMC) that correlates with delayed repair of MMC-induced chromosomal DNA damage monitored by pulsed-field gel electrophoresis. Genetic epistasis analysis in Hfx. volcanii suggests that NreA works together with the UvrABC proteins in repairing DNA damage resulting from exposure to MMC. The wide distribution of NreA family members implies an important role for the protein in DNA damage repair in all archaeal lineages.