Department of Biology, Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA.
Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, USA.
Environ Microbiol. 2020 Oct;22(10):4167-4182. doi: 10.1111/1462-2920.14763. Epub 2019 Aug 16.
The opportunistic human pathogen Vibrio vulnificus inhabits warm coastal waters and asymptomatically colonizes seafood, most commonly oysters. We previously characterized an isolate that exhibited greater biofilm formation, aggregation and oyster colonization than its parent. This was due, in part, to the production of a Type IV Tad pilus (Iam). However, the locus lacked key processing and regulatory genes required for pilus production. Here, we identify a pilin peptidase iamP, and LysR-type regulator (LRTR) iamR, that fulfil these roles and show that environmental calcium, which oysters enrich for shell repair and growth, regulates iam expression. The architecture of the iam locus differs from the classical LRTR paradigm and requires an additional promoter to be integrated into the regulatory network. IamR specifically recognized the iamR promoter (P ) and the intergenic iamP-iamA region (P ). P exhibited classical negative auto-regulation but, strikingly, IamR inversely regulated the divergent iamP and iamA promoters in a calcium-dependent manner. Moreover, expression of the c-di-GMP and calcium-regulated, biofilm-promoting brp exopolysaccharide was IamA-dependent. These results support a scenario in which the calcium-enriched oyster environment triggers IamP-mediated processing of prepilin amassed in the periplasm for rapid pilin elaboration and subsequent BRP production to promote colonization.
机会性病原体创伤弧菌栖息于温暖的沿海水域，无症状地定植于海鲜中，最常见的是牡蛎。我们之前描述了一个分离株，它比其亲本具有更强的生物膜形成、聚集和牡蛎定植能力。这部分归因于 IV 型 Tad 菌毛（Iam）的产生。然而，该基因座缺乏产生菌毛所需的关键加工和调节基因。在这里，我们鉴定了一种纤毛肽酶 iamP 和 LysR 型调节因子（LRTR）iamR，它们发挥了这些作用，并表明牡蛎富集壳修复和生长所需的环境钙调节 iam 的表达。iam 基因座的结构不同于经典的 LRTR 范例，需要额外的启动子才能整合到调控网络中。iamR 特异性识别 iamR 启动子（P ）和基因间 iamP-iamA 区域（P ）。P 表现出经典的负自动调节，但引人注目地是，iamR 以钙依赖性方式反向调节分歧的 iamP 和 iamA 启动子。此外，c-di-GMP 和钙调节的生物膜促进 brp 外多糖的表达依赖于 IamA。这些结果支持了这样一种情景，即富含钙的牡蛎环境触发了 IamP 介导的周质中预菌毛的加工，以便快速产生菌毛，随后产生 BRP 促进定植。
