Vibrio cholerae is the causative agent of the diarrheal disease cholera, for which biofilm communities are considered to be environmental reservoirs. In endemic regions, and after algal blooms, which may result from phosphate enrichment following agricultural runoff, the bacterium is released from biofilms resulting in seasonal disease outbreaks. However, the molecular mechanism by which V. cholerae senses its environment and switches lifestyles from the biofilm-bound state to the planktonic state is largely unknown. Here, we report that the major biofilm scaffolding protein RbmA undergoes autocatalytic proteolysis via a phosphate-dependent induced proximity activation mechanism. Furthermore, we show that RbmA mutants that are defective in autoproteolysis cause V. cholerae biofilms to grow larger and mechanically stronger, correlating well with the observation that RbmA stability directly affects microbial community homeostasis and rheological properties. In conclusion, our biophysical study characterizes a novel phosphate-dependent breakdown pathway of RbmA, while microbiological data suggest a new, sensory role of this biofilm scaffolding element.

中文翻译：

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霍乱弧菌生物膜支架蛋白 RbmA 显示出内在的、磷酸盐依赖性的自身蛋白水解活性

霍乱弧菌是腹泻病霍乱的病原体，生物膜群落被认为是环境宿主。在流行地区，以及可能由农业径流后磷酸盐富集引起的藻类大量繁殖后，细菌从生物膜中释放出来，导致季节性疾病爆发。然而，霍乱弧菌感知其环境并将生活方式从生物膜结合状态转变为浮游状态的分子机制在很大程度上是未知的。在这里，我们报告了主要的生物膜支架蛋白 RbmA 通过磷酸盐依赖性诱导的邻近激活机制进行自催化蛋白水解。此外，我们表明，自体蛋白水解缺陷的 RbmA 突变体导致霍乱弧菌生物膜变得更大且机械强度更高，与 RbmA 稳定性直接影响微生物群落稳态和流变特性的观察结果密切相关。总之，我们的生物物理研究表征了 RbmA 的一种新的磷酸盐依赖性分解途径，而微生物学数据表明这种生物膜支架元件具有新的感官作用。