Comparative genomic analysis result tables.

The facultative human pathogen, Vibrio cholerae, employs two-component signal transduction systems (TCS) to sense and respond to environmental signals encountered during its infection cycle. TCSs consist of a sensor histidine kinase (HK) and a response regulator (RR); the V. cholerae genome encodes 43 HKs and 49 RRs, of which 25 are predicted to be cognate pairs. Using deletion mutants of each HK gene, we analyzed the transcription of vpsL, a biofilm gene required for Vibrio polysaccharide and biofilm formation. We found that a V. cholerae TCS that had not been studied before, now termed Rvv, controls biofilm gene transcription. The Rvv TCS is part of a three-gene operon that is present in 30% of Vibrionales species. The rvv operon encodes RvvA, the HK; RvvB, the cognate RR; and RvvC, a protein of unknown function. Deletion of rvvA increased transcription of biofilm genes and altered biofilm formation, while deletion of rvvB or rvvC lead to no changes in biofilm gene transcription. The phenotypes observed in ΔrvvA depend on RvvB. Mutating RvvB to mimic constitutively active and inactive versions of the RR only impacted phenotypes in the ΔrvvA genetic background. Mutating the conserved residue required for kinase activity in RvvA did not affect phenotypes, whereas mutation of the conserved residue required for phosphatase activity mimicked the phenotype of the rvvA mutant. Furthermore, ΔrvvA displayed a significant colonization defect which was dependent on RvvB and RvvB phosphorylation state, but not on VPS production. We found that RvvA’s phosphatase activity regulates biofilm gene transcription, biofilm formation, and colonization phenotypes. This is the first systematic analysis of the role of V. cholerae HKs in biofilm gene transcription and resulted in the identification of a new regulator of biofilm formation and virulence, advancing our understanding of the role TCSs play in regulating these critical cellular processes in V. cholerae.

兼性人类致病菌霍乱弧菌（Vibrio cholerae）借助双组分信号转导系统（two-component signal transduction systems, TCS）感知并响应其感染周期中遭遇的环境信号。双组分信号转导系统由组氨酸激酶传感器（sensor histidine kinase, HK）与应答调节蛋白（response regulator, RR）组成；霍乱弧菌基因组编码43种HK与49种RR，其中25对被预测为同源配对。本研究通过构建每个HK基因的缺失突变株，分析了vpsL的转录水平——vpsL是一种参与弧菌多糖合成与生物膜形成的生物膜相关基因。我们发现了一种此前未被研究的霍乱弧菌TCS，将其命名为Rvv，该系统可调控生物膜基因的转录。Rvv TCS属于一个三基因操纵子的一部分，该操纵子存在于30%的弧菌目（Vibrionales）物种中。rvv操纵子编码HK RvvA、同源配对RR RvvB，以及功能未知蛋白RvvC。缺失rvvA会提升生物膜基因的转录水平并改变生物膜形成模式，而缺失rvvB或rvvC则不会对生物膜基因的转录产生影响。ΔrvvA菌株中观察到的表型依赖于RvvB。将RvvB突变以模拟组成型激活与非激活形式的RR时，仅在ΔrvvA的遗传背景下会对表型产生影响。对RvvA中激酶活性所需的保守残基进行突变，不会对表型产生影响；而对磷酸酶活性所需的保守残基进行突变，则可模拟rvvA缺失突变株的表型。此外，ΔrvvA菌株表现出显著的定殖缺陷，该缺陷依赖于RvvB及其磷酸化状态，而非弧菌多糖的合成。我们发现RvvA的磷酸酶活性可调控生物膜基因转录、生物膜形成与定殖相关表型。本研究首次系统分析了霍乱弧菌HK在生物膜基因转录中的作用，并鉴定出一种全新的生物膜形成与毒力调控因子，加深了我们对TCS在霍乱弧菌调控上述关键细胞过程中所发挥作用的理解。