Pleiotropic functions of glutathione in the adaptive response to long-term nitrogen starvation in Escherichia coli

Abstract

Nitrogen (N) is essential for bacterial growth, and adaptation to N starvation involves extensive reprogramming of gene expression. A hallmark subcellular feature in long-term N starved Escherichia coli cells is the presence of biomolecular condensates of the major bacterial RNA regulator Hfq. The Hfq condensates, which accumulate gradually during N starvation, contribute to adaptation by modulating RNA metabolism and central metabolic pathways. Metabolites play central roles in stress responses, often acting as modulators of protein function to support survival and recovery. Glutathione (GSH), a universal stress protectant, has broad roles in bacterial stress adaptation, yet its function during N starvation remains unexplored. Using a GSH-deficient mutant ({Delta}gshAB), we show that GSH is required for optimal survival and recovery from prolonged N starvation. We reveal that GSH regulates the temporal dynamics of Hfq condensation and dissipation during starvation and recovery, respectively, via an as-yet unknown mechanism. Notably, these two functions of GSH appear mutually exclusive, highlighting its pleiotropic role in the adaptive response to N starvation that potentially extends its canonical function as a stress protectant. IMPORTANCENitrogen is a vital nutrient that bacteria need to grow. When nitrogen becomes scarce, bacteria must quickly adjust how their genes are used to survive. In Escherichia coli, one of the key changes during long-term nitrogen starvation is the formation of tiny structures inside the cell called Hfq condensates, which help manage genetic information flow and metabolism. Small molecules called metabolites play important roles in helping bacteria cope with stress, and one such molecule, glutathione (GSH), is known to protect cells under various stress conditions. However, its role during nitrogen starvation is not known. In this study, we used a mutant strain of E. coli that cannot produce GSH and found that these bacteria struggle to survive and recover from nitrogen starvation. We also discovered that GSH helps control when and how Hfq condensates form and disappear. Although, these two functions of GSH seem to be unrelated, our study highlights the versatile role of GSH in helping bacteria adapt to nitrogen stress.