RdmA Is a Key Regulator in Autoinduction of DSF Quorum Quenching in Pseudomonas nitroreducens HS-18.
RdmA Is a Key Regulator in Autoinduction of DSF Quorum Quenching in Pseudomonas nitroreducens HS-18.
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RdmA 是硝基还原假单胞菌 HS-18 中 DSF 群体淬灭自诱导的关键调节剂
作者：
扩散信号因子（Diffusible Signal Factor，DSF）是一个广泛保守的群体感应（quorum-sensing，QS）信号家族，在许多革兰氏阴性细菌病原体中调节毒力因子的产生和致病性。我们最近报道了一种高效的DSF淬灭细菌分离株，硝基还原假单胞菌HS-18，其中含有一个操纵子，该操纵子具有四个DSF诱导基因，digABCD或digA-D，负责DSF信号的降解。然而，管理digA-D响应DSF诱导的调节机制尚未被表征。在这项研究中，我们确定了一种新的转录调节因子，我们命名为RdmA（调节DSF代谢），负调控digA-D的表达和抑制DSF降解。此外，我们发现位于rdmA附近的基因簇也受到RdmA的负调控，并在DSF降解中发挥关键作用，因此将该簇命名为dmg（DSF代谢基因）。电泳迁移率变动分析和遗传分析表明，RdmA抑制dmg基因的转录表达的直接方式。进一步的研究表明，DSF作为拮抗剂与RdmA结合，从而消除RdmA与靶启动子的结合及其对dmg基因转录表达的抑制。总之，这项研究的结果揭示了一个中央调节器和一个与P. nitroreducens HS-18中DSF降解的自诱导相关的基因簇，这将有助于理解这种有效生物防治剂的群体淬灭活性的遗传基础和调控机制。
Diffusible signal factor (DSF) represents a family of widely conserved quorum-sensing (QS) signals which regulate virulence factor production and pathogenicity in numerous Gram-negative bacterial pathogens. We recently reported the identification of a highly potent DSF-quenching bacterial isolate, Pseudomonas nitroreducens HS-18, which contains an operon with four DSF-inducible genes, digABCD, or digA–D, that are responsible for degradation of DSF signals. However, the regulatory mechanisms that govern the digA–D response to DSF induction have not yet been characterized. In this study, we identified a novel transcriptional regulator we designated RdmA (regulator of DSF metabolism) which negatively regulates the expression of digA–D and represses DSF degradation. In addition, we found that a gene cluster located adjacent to rdmA was also negatively regulated by RdmA and played a key role in DSF degradation; this cluster was hence named dmg (DSF metabolism genes). An electrophoretic mobility shift assay and genetic analysis showed that RdmA represses the transcriptional expression of the dmg genes in a direct manner. Further studies demonstrated that DSF acts as an antagonist and binds to RdmA, which abrogates RdmA binding to the target promoter and its suppression on transcriptional expression of the dmg genes. Taken together, the results from this study have unveiled a central regulator and a gene cluster associated with the autoinduction of DSF degradation in P. nitroreducens HS-18, and this will aid in the understanding of the genetic basis and regulatory mechanisms that govern the quorum-quenching activity of this potent biocontrol agent.
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