No abstract

Excessive amounts of reactive oxygen species (ROS) can cause irreversible damages to essential cellular components such as DNA. Genetically encoded biosensors targeting oxidative stress and DNA-stress have emerged to a powerful analytical tool to assess physiological states in a non-invasive manner. In this study, we aimed to combine the redox biosensor protein Mrx1-roGFP2 with a transcriptional biosensor for DNA-damage based on the PrecA promoter fused to a reporter gene (e2-crimson) in Corynebacterium glutamicum. Therefore, the redox biosensor strains C. glutamicum WT_Mrx1-roGFP2 and the mycothiol (MSH)-deficient mutant strain C. glutamicum ΔmshC_Mrx1-roGFP2 were equipped with the DNA-stress reporter plasmid pJC1_PrecA_e2-crimson. Exposure of the double-sensor equipped C. glutamicum WT strain to hypochlorite resulted in an oxidative redox shift, accompanied by an induction of the DNA-stress reporter system. In absence of the major non-enzymatic antioxidant MSH, the induction of the DNA-stress response was even more pronounced. This confirms the linkage of oxidative stress and DNA-damage response, and therefore making antioxidants a crucial player to protect DNA. Furthermore, exposure of the double biosensor strains to a DNA-damage inducing agent resulted in an oxidative redox shift. These results suggest a direct link of DNA-damage and oxidative stress response in C. glutamicum. Finally, we observed that inhibition of cell wall biosynthesis by penicillin caused both an oxidative redox shift and a DNA-damage response in C. glutamicum. The excellent compatibility of Mrx1-roGFP2 with E2-Crimson shown here provides a powerful combinatorial biosensor concept for in-depth studies of redox-related physiology in future studies.

Corynebacterium glutamicum efficiently produces glutamate when growth is inhibited. Analyses of viability in this non-growing state requires time consuming plating and determination of colony forming units. We here establish impedance flow cytometry measurements to assess the viability of non-growing, glutamate producing C. glutamicum cultures within minutes.