Cross-regulation of amino acid synthesis and anaerobic electron transfer by MetR-mediated methionine signaling

However, the molecular mechanisms underlying this balance remain poorly understood. Here, we report a mechanism cross-regulating amino acid biosynthesis and anaerobic respiration in bacterial cells.

Using the model bacterium Shewanella oneidensis MR-1, we demonstrated that methionine activates extracellular electron transfer activity at submillimolar concentrations. This regulation is mediated by the transcription factor MetR, a canonical regulator of methionine biosynthesis. Under methionine-limited conditions, MR-1 upregulates methionine biosynthesis genes while repressing genes involved in extracellular electron transfer (metal reduction) and other anaerobic respiratory processes.