Cyclic di-GMP triggers the hypoxic adaptation of Mycobacterium bovis through a metabolic switching regulator ArgR

During infection, intracellular pathogens inevitably face the pressure of hypoxia. Mycobacterium tuberculosis and Mycobacterium bovis represent two typical intracellular bacteria, but the signalling pathway of their adaptation to hypoxia remains unclear. Here, we report a new mechanism of the hypoxic adaptation in M. bovis driven by the second messenger molecule c-di-GMP. We found that c-di-GMP was significantly accumulated in bacterial cells under hypoxic stress and blocked the inhibitory activity of ArgR, an arginine metabolism gene cluster regulator, which increased arginine synthesis and slowed tricarboxylic acid cycle (TCA cycle) and aerobic respiration. Meanwhile, c-di-GMP relieved the self-inhibition of argR expression, and ArgR could interact with the nitrite metabolic gene regulator Cmr, promoting the positive regulation of Cmr and, thereafter, the nitrite respiration. Consistently, c-di-GMP significantly induced the expression of arginine and nitrite metabolism gene clusters and increased the mycobacterial survival ability under hypoxia. Therefore, we found a new function of the second messenger molecule c-di-GMP and characterized ArgR as a metabolic switching regulator that can coordinate the c-di-GMP signal to trigger hypoxic adaptation in mycobacteria. Our findings provide a potential new target for blocking the life cycle of M. tuberculosis infection.