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

Abstract

The transition of Vibrio cholerae 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 ΔdegS 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 σE 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 V. cholerae environmental adaptation and highlighting a potential target within its transmission chain.