A nutrient-sensing protease DegS suppresses biofilm formation in Vibrio cholerae via the CdgH-c-di-GMP-VpsR axis under nutrient limitation.

The transition of from the host intestine to oligotrophic aquatic environments presents a severe nutrient downshift, yet the upstream sensory mechanism that triggers adaptive biofilm formation remains unclear. Here, we identify the periplasmic protease DegS as a critical nutrient-responsive regulator that suppresses biofilm development under low-nutrient conditions. We demonstrate that a mutant exhibits robust biofilm formation, enhanced antibiotic tolerance, and significantly increased colonization on environmentally relevant surfaces such as microplastics. Strikingly, this regulation is independent of the canonical σ stress pathway. Instead, we elucidate a novel signalling axis wherein DegS negatively regulates the diguanylate cyclase CdgH. Loss of DegS relieves this inhibition, leading to elevated cellular c-di-GMP levels, which in turn activates the master transcriptional regulator VpsR, upregulating biofilm matrix gene expression. This DegS-CdgH-c-di-GMP-VpsR pathway is functional not only in minimal medium but also in simulated natural aquatic environments. Our findings reveal DegS as a key upstream sensor that translates nutrient scarcity into a precise inhibitory signal via c-di-GMP-dependent transcription, providing new insights into the molecular basis of environmental adaptation and highlighting a potential target within its transmission chain.