CpxR-Dependent Thermoregulation of Serratia marcescens PrtA Metalloprotease Expression and Its Contribution to Bacterial Biofilm Formation
CpxR-Dependent Thermoregulation of Serratia marcescens PrtA Metalloprotease Expression and Its Contribution to Bacterial Biofilm Formation
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DOI：
10.1128/jb.00006-18
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发表时间：
2018-04-01
影响因子：
3.2
通讯作者：
Garcia Vescovi, Eleonora
中科院分区：
文献类型：
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作者：
Bruna, Roberto E.;Victoria Molino, Maria;Garcia Vescovi, Eleonora
PrtA 是粘质沙雷氏菌主要分泌的金属蛋白酶。之前的报道表明 PrtA 与这种细菌的致病能力有关。 PrtA 在临床上也被用作有效的镇痛和抗炎药物，其催化特性引起了工业界的兴趣。相比之下，人们对沙雷氏菌中 PrtA 表达的生理控制机制知之甚少。在这项工作中，我们证明当细菌生长温度从 37 摄氏度降低到 30 摄氏度时，PrtA 的产生会受到抑制。我们表明这种温度调节发生在转录水平。我们确定 prtA 的上游有一个保守基序，可以被 CpxR 转录调节因子直接识别。这一特征在沙雷氏菌菌株中被发现，无论其分离来源如何，表明依赖于 CpxR 的 PrtA 表达调节具有进化保守性。我们发现，在 S. marcescens 中，CpxAR 系统在 37°C 时比在 30°C 时更活跃。与这些结果非常一致，在 cpxR 突变体背景中，prtA 在 37°C 时被去抑制，而 NlpE 脂蛋白（一种众所周知的 CpxAR 诱导条件）的过度表达会抑制 PrtA 表达，这表明 CpxR 激活形式的水平 在 37 摄氏度时比在 30 摄氏度时有所增加。此外，我们确定 PrtA 与粘质沙门氏菌形成生物膜的能力有关。因此，只有当细菌在 37 摄氏度下生长时，CpxR 才会影响生物膜表型。总之，我们的研究结果揭示了微调 PrtA 表达的调节机制，并揭示了 PrtA 在粘质沙门氏菌生活方式中的新作用。重要性我们证明，粘质沙门氏菌金属蛋白酶 PrtA 表达是转录温度调节的。虽然在 30 摄氏度以下强烈激活，但其表达在 37 摄氏度时下调。我们发现，在粘质沙门氏菌中，响应包膜应激和细菌表面粘附的 CpxAR 信号转导系统在 37 摄氏度时被激活，并能够通过 CpxR 与位于 prtA 基因上游的结合基序直接相互作用来下调 PrtA 表达。此外，我们发现，无论细菌生长温度如何，PrtA 表达都有利于粘质沙门氏菌形成生物膜的能力。在这种情况下，温度调节以及高度保守的 CpxR 依赖性调节机制提供了有关 PrtA 作为与粘质沙门氏菌在非生物表面上的持久性和细菌宿主定殖能力有关的因素的相关性的线索。
PrtA is the major secreted metalloprotease of Serratia marcescens. Previous reports implicate PrtA in the pathogenic capacity of this bacterium. PrtA is also clinically used as a potent analgesic and anti-inflammatory drug, and its catalytic properties attract industrial interest. Comparatively, there is scarce knowledge about the mechanisms that physiologically govern PrtA expression in Serratia. In this work, we demonstrate that PrtA production is derepressed when the bacterial growth temperature decreases from 37 degrees C to 30 degrees C. We show that this thermoregulation occurs at the transcriptional level. We determined that upstream of prtA, there is a conserved motif that is directly recognized by the CpxR transcriptional regulator. This feature is found along Serratia strains irrespective of their isolation source, suggesting an evolutionary conservation of CpxR-dependent regulation of PrtA expression. We found that in S. marcescens, the CpxAR system is more active at 37 degrees C than at 30 degrees C. In good agreement with these results, in a cpxR mutant background, prtA is derepressed at 37 degrees C, while overexpression of the NlpE lipoprotein, a well-known CpxAR-inducing condition, inhibits PrtA expression, suggesting that the levels of the activated form of CpxR are increased at 37 degrees C over those at 30 degrees C. In addition, we establish that PrtA is involved in the ability of S. marcescens to develop biofilm. In accordance, CpxR influences the biofilm phenotype only when bacteria are grown at 37 degrees C. In sum, our findings shed light on regulatory mechanisms that fine-tune PrtA expression and reveal a novel role for PrtA in the lifestyle of S. marcescens.IMPORTANCE We demonstrate that S. marcescens metalloprotease PrtA expression is transcriptionally thermoregulated. While strongly activated below 30 degrees C, its expression is downregulated at 37 degrees C. We found that in S. marcescens, the CpxAR signal transduction system, which responds to envelope stress and bacterial surface adhesion, is activated at 37 degrees C and able to downregulate PrtA expression by direct interaction of CpxR with a binding motif located upstream of the prtA gene. Moreover, we reveal that PrtA expression favors the ability of S. marcescens to develop biofilm, irrespective of the bacterial growth temperature. In this context, thermoregulation along with a highly conserved CpxR-dependent modulation mechanism gives clues about the relevance of PrtA as a factor implicated in the persistence of S. marcescens on abiotic surfaces and in bacterial host colonization capacity.