Abstract

Oxidative stress is an unavoidable consequence of interactions with various reactive oxygen species (ROS)-inducing agents that would damage cells or even cause cell death. Bacteria have developed defensive systems, including induction of stress-sensing proteins and detoxification enzymes, to handle oxidative stress. Cyclic diguanylate (c-di-GMP) is a ubiquitous intracellular bacterial second messenger that coordinates diverse aspects of bacterial growth and behavior. In this study, we revealed a mechanism by which c-di-GMP regulated bacterial oxidative stress resistance in Pseudomonas putida KT2440. High c-di-GMP level was found to enhance bacterial resistance towards hydrogen peroxide. Transcription assay showed that expression of two oxidative stress resistance genes, fpr-1 and katE , was promoted under high c-di-GMP level. Deletion of fpr-1 and katE both decreased bacterial tolerance to hydrogen peroxide and weakened the effect of c-di-GMP on oxidative stress resistance. The promoted expression of fpr-1 under high c-di-GMP level was caused by increased cellular ROS via a transcriptional regulator FinR. We further demonstrated that the influence of high c-di-GMP on cellular ROS depend on the existence of FleQ, a transcriptional regulatory c-di-GMP effector. Besides, the regulation of katE by c-di-GMP was also FleQ dependent in an indirect way. Our results proved a connection between c-di-GMP and oxidative stress resistance and revealed a mechanism by which c-di-GMP regulated expression of fpr-1 and katE in P. putida KT2440.