Frando Andrew, Parsek Robert S, Omar Jamal, Smalley Nicole E, Dandekar Ajai A
Department of Medicine, University of Washington, Seattle, WA 98195 USA.
Department of Microbiology, University of Washington, Seattle, WA 98195 USA.
bioRxiv. 2025 Mar 17:2025.03.17.643737. doi: 10.1101/2025.03.17.643737.
uses quorum sensing (QS), a cell-cell communication system that enables it to sense cell density and to alter gene expression. has three complete QS circuits controlled by the regulators LasR, RhlR, and PqsR, that together activate hundreds of genes. In the well-studied strain PAO1, QS is organized hierarchically, with PqsR and RhlR activity dependent on LasR. This hierarchy depends on the non-QS transcription factor MexT; deletion of allows for RhlR activity in the absence of LasR. We aimed to identify how MexT modulates the QS architecture. We compared the transcriptome of PAO1 to that of PAO1Δ and determined a MexT regulon. We identified two MexT-regulated operons that may affect the QS hierarchy: the efflux pump genes - and the quinolone signal (PQS) synthesis genes . We tested whether the products of these genes affected the QS hierarchy. A knockout mutant, like a deletion mutant, exhibited RhlR activity earlier, and to a higher magnitude, than wild-type PAO1. MexEF-OprN is known to export quinolones, and we found that exogenous addition of PQS, through PqsE, also resulted in earlier and higher magnitude of RhlR activity compared to wild-type PAO1. We also discovered alternate QS architectures in clinical isolates, where RhlR activity is not fully dependent on LasR. In these isolates, surprisingly, MexT does not influence the relationship between LasR and RhlR. Our work reveals a new suite of factors that regulate QS in , with implications for bacterial behaviors in environmental and clinical settings.
利用群体感应（QS），这是一种细胞间通信系统，使其能够感知细胞密度并改变基因表达。有三个由调节因子LasR、RhlR和PqsR控制的完整QS回路，它们共同激活数百个基因。在经过充分研究的菌株PAO1中，QS是分层组织的，PqsR和RhlR的活性依赖于LasR。这种层次结构依赖于非QS转录因子MexT；删除MexT可使RhlR在没有LasR的情况下具有活性。我们旨在确定MexT如何调节QS结构。我们将PAO1的转录组与PAO1Δ的转录组进行比较，并确定了MexT调控子。我们鉴定出两个可能影响QS层次结构的受MexT调控的操纵子：外排泵基因MexEF - OprN和喹诺酮信号（PQS）合成基因pqsABCDE。我们测试了这些基因的产物是否影响QS层次结构。MexEF - OprN敲除突变体，与MexT缺失突变体一样，比野生型PAO1更早且更高程度地表现出RhlR活性。已知MexEF - OprN可输出喹诺酮类物质，并且我们发现通过PqsE外源添加PQS，与野生型PAO1相比，也导致更早且更高程度的RhlR活性。我们还在临床分离株中发现了替代的QS结构模式，其中RhlR活性并不完全依赖于LasR。令人惊讶的是，在这些分离株中，MexT并不影响LasR和RhlR之间的关系。我们的工作揭示了一组新的调节铜绿假单胞菌QS的因子，这对细菌在环境和临床环境中的行为具有重要意义。
