Project description:The ability of Pseudomonas aeruginosa to detect host immune responses and coordinate the production of virulence factors is crucial for its high pathogenicity. However, the regulatory mechanisms underlying this process remain largely unknown. In this study, we extensively characterize the conserved two-component system CprRS in P. aeruginosa and uncover the role of the sensor histidine kinase CprS as a receptor for the human host defense peptide LL-37, thereby modulating bacterial virulence. In the presence of LL-37, CprS functions as a phosphatase, targeting the intracellular activator CprR for phosphorylation at position D53, ultimately leading to CprR activation. By employing quantitative proteomics and transcription analysis, we further elucidate that CprR induction under LL-37 treatment promotes the expression of type III secretion system effectors. This, in turn, impedes the expression of proinflammatory cytokines and significantly increases bacterial cytotoxicity towards macrophages. Notably, the mutation of either cprS or cprR markedly diminishes bacterial survival in both macrophage and insect infection models. Collectively, our study uncovers a novel regulatory mechanism of the two-component system in P. aeruginosa, which enables the bacterium to sense and respond to human innate immune system responses while ensuring a timely balance of virulence genes.
Project description:Pseudomonas aeruginosa is a common nosocomial pathogen which produces siderophores to solubilize and transport chelated Fe3+ to aid its survival in both the environment and the host. However, there is a lack of comprehensive understanding regarding the molecular mechanisms underlying siderophore synthesis, uptake, and regulation within various ecological niches. In this study, we demonstrated that the BfmRS two-component system, part of the core genome of P. aeruginosa, plays a crucial role in siderophore metabolism. We have identified BfmS as an osmosensing histidine kinase that responds to external osmolytes, then modulates the activation of the response regulator BfmR. Under high osmolality, BfmR could directly bind to the promoters of pvd, fpv, and femARI gene clusters, thereby enhancing their expression and promoting siderophore metabolism. The proteomic and phenotypic analyses confirmed that deletion of bfmRS results in reduced expression levels of siderophore-related proteins as well as siderophore production. Importantly, loss of bfmR or bfmS significantly impaired bacterial survival in both iron deficiency medium and mouse lung infection models. Furthermore, phylogenetic analysis revealed that BfmRS is highly conserved and widely distributed across Pseudomonas species, evidences also proved that the BfmR of P. putida KT2440 and P. sp. MRSN12121 activated siderophore genes in response to high osmolality. Overall, this study sheds light on the previously unexplored signal transduction pathway, BfmRS, which governs the siderophore regulation in Pseudomonas species through perceiving an osmotic upshift. Considering that siderophores serve as unique social mediators, our findings contribute to a better understanding of how siderophores facilitate bacterial interactions with their eukaryotic hosts and contribute to the establishment of stable communities.
Project description:Two component systems (TCSs) control a large proportion of virulence factors in Pseudomonas aeruginosa. Yet, investigations on inhibitors of regulatory pathways of TCS remain scare, despite their potential in anti-virulence strategies. This work encompasses the working mechanism of PIT4, a protein derived from the lytic P. aeruginosa phage LSL4. This viral protein inhibits bacterial motility and in particular twitching motility, while reducing the virulence of P. aeruginosa towards HeLa cells. Via differential gene expression and a yeast two-hybrid screen, PIT4 was shown to interact with components of different two component systems. In one-on-one interaction assays, it was confirmed that PIT4 interacts with the histidine kinases FleS, PilS and PA2882, through interaction with the histidine kinase domain. As such, this work highlights the potential of previously unknown phage proteins in virulence regulation of multidrug resistant pathogens that might be exploited for anti-virulence strategies and biotechnological applications.
Project description:Microarray were done on 4 independent cultures. PA01 was grown for 6 hours to late log growth phase (OD600 0.9-1.0) in liquid BM2-swarming media under shaking conditions(swimming) or for 18 hours at 37C on BM2-swarming plate containing 0.5% (w/v) agar and 0.1% casamino acids. Cells were harvested either by centrifugation(swimming) or by a sterile inoculating loop (swarming) and were resuspended n BM2-swarming media supplement with RNAprotect reagent (Qiagen)
Project description:Substrains in Escherichia coli K-12 MG1655 can possess various swimming motility, which is mostly resulted from different expression levels of flhDC. Here, we studied the swimming motility of two MG1655 substrains, CY562 and CY570. Our results showed that CY562 had no insertion at the promoter region of flhDC and possessed no swimming motility. In contrast, CY570 had an IS-element insertion at the promoter region of flhDC and showed a hyper-motile phenotype. Transcriptomic data suggest that expression of flhDC and the other known flagella genes was much lower in CY562 than that in CY570. Moreover, CY562 possessed higher expression levels for genes involved in stress response, especially acid-stress response, than CY570. Consistently, CY562 showed a higher survival rate under acid stress than CY570. Our data indicate that there are mechanisms conversely regulating motility and stress response in E. coli.