Loss of RNA chaperone Hfq unveils a toxic pathway in Pseudomonas aeruginosa

Hfq is an RNA chaperone that serves as a master regulator of bacterial physiology. Here we show that in the opportunistic pathogen Pseudomonas aeruginosa, the loss of Hfq can result in a dramatic reduction in growth in a manner that is dependent upon MexT, a transcription regulator that governs antibiotic resistance in this organism. Using a combination of chromatin immunoprecipitation with high-throughput sequencing and transposon insertion sequencing we identify MexT-activated genes responsible for mediating the growth defect of hfq mutant cells. These include a newly identified MexT-controlled gene we call hilR. We demonstrate that hilR encodes a small protein that is acutely toxic to wild-type cells when produced ectopically. Furthermore, we show that hilR expression is negatively regulated by Hfq, offering a possible explanation for the growth defect of hfq mutant cells. Finally, we present evidence that the expression of MexT-activated genes is dependent upon GshA, an enzyme involved in the synthesis of glutathione. Our findings suggest that Hfq can influence the growth of P. aeruginosa by limiting the toxic effects of specific MexT-regulated genes. Moreover, our results identify glutathione as a factor important for the in vivo activity of MexT.

Hfq是一种RNA分子伴侣（RNA chaperone），可作为细菌生理过程的主调控因子。本研究针对机会致病菌铜绿假单胞菌（Pseudomonas aeruginosa）展开，发现Hfq的缺失会导致其生长能力显著下降，且该表型依赖于MexT——一种调控该菌抗生素耐药性的转录调控因子。本研究结合染色质免疫共沉淀联合高通量测序与转座子插入测序技术，鉴定出了介导hfq突变体细胞生长缺陷的MexT激活型基因，其中包括一个新鉴定的、受MexT调控的基因，我们将其命名为hilR。实验证实，hilR编码一种小型蛋白，当异位表达该蛋白时，会对野生型细胞产生强烈毒性。此外，研究发现hilR的表达受到Hfq的负向调控，这为解释hfq突变体细胞的生长缺陷提供了潜在机制。最后，本研究证实MexT激活型基因的表达依赖于GshA——一种参与谷胱甘肽合成的酶。本研究结果表明，Hfq可通过抑制特定MexT调控基因的毒性作用，影响铜绿假单胞菌的生长。此外，本研究揭示谷胱甘肽是影响MexT体内活性的关键因子。