Department of Molecular Biology, Princeton University, Princeton, NJ, Unites States of America.
Department of Chemistry, Princeton University, Princeton, NJ, Unites States of America.
PLoS Pathog. 2020 Sep 14;16(9):e1008867. doi: 10.1371/journal.ppat.1008867. eCollection 2020 Sep.
Surface attachment, an early step in the colonization of multiple host environments, activates the virulence of the human pathogen P. aeruginosa. However, the downstream toxins that mediate surface-dependent P. aeruginosa virulence remain unclear, as do the signaling pathways that lead to their activation. Here, we demonstrate that alkyl-quinolone (AQ) secondary metabolites are rapidly induced upon surface association and act directly on host cells to cause cytotoxicity. Surface-induced AQ cytotoxicity is independent of other AQ functions like quorum sensing or PQS-specific activities like iron sequestration. We further show that packaging of AQs in outer-membrane vesicles (OMVs) increases their cytotoxicity to host cells but not their ability to stimulate downstream quorum sensing pathways in bacteria. OMVs lacking AQs are significantly less cytotoxic, suggesting these molecules play a role in OMV cytotoxicity, in addition to their previously characterized role in OMV biogenesis. AQ reporters also enabled us to dissect the signal transduction pathways downstream of the two known regulators of surface-dependent virulence, the quorum sensing receptor, LasR, and the putative mechanosensor, PilY1. Specifically, we show that PilY1 regulates surface-induced AQ production by repressing the AlgR-AlgZ two-component system. AlgR then induces RhlR, which can induce the AQ biosynthesis operon under specific conditions. These findings collectively suggest that the induction of AQs upon surface association is both necessary and sufficient to explain surface-induced P. aeruginosa virulence.
表面附着是人体病原体铜绿假单胞菌在多种宿主环境中定植的早期步骤，它能激活铜绿假单胞菌的毒力。然而，介导表面依赖的铜绿假单胞菌毒力的下游毒素以及导致其激活的信号通路仍不清楚。在这里，我们证明烷基-喹诺酮（AQ）次生代谢物在表面结合后迅速诱导，并直接作用于宿主细胞引起细胞毒性。表面诱导的 AQ 细胞毒性不依赖于其他 AQ 功能，如群体感应或 PQS 特异性活性，如铁螯合。我们进一步表明，AQ 在外膜囊泡（OMV）中的包装增加了它们对宿主细胞的细胞毒性，但不增加它们刺激细菌中下游群体感应途径的能力。缺乏 AQs 的 OMVs 的细胞毒性显著降低，这表明这些分子在 OMV 细胞毒性中起作用，除了它们在 OMV 生物发生中已被描述的作用之外。AQ 报告基因还使我们能够剖析两种已知的表面依赖性毒力调节因子（群体感应受体 LasR 和假定的机械感受器 PilY1）下游的信号转导途径。具体来说，我们表明 PilY1 通过抑制 AlgR-AlgZ 双组分系统来调节表面诱导的 AQ 产生。AlgR 然后诱导 RhlR，在特定条件下，RhlR 可以诱导 AQ 生物合成操纵子。这些发现共同表明，表面附着后 AQs 的诱导既是必要的，也是充分的，足以解释表面诱导的铜绿假单胞菌毒力。
