tRNA modification enzyme MiaB connects environmental cues to activation of Pseudomonas aeruginosa type III secretion system

Combined Prokaryotic Transcriptomics and Proteomics Analysis of Clinical Trueperella pyogenes Isolates with Distinctive Cytotoxicity

Trueperella pyogenes is a widely distributed opportunistic pathogenic bacterium that can infect livestock, wildlife, community animals, and humans, resulting in suppurative infection of tissue and organ mucosa, including pneumonia, liver abscessation, mastitis, metritis, endocarditis, and osteoarthritis. TP1804 and TP1808 were isolated from the uterine lavage fluid of cows with endometritis. This study analyzed the prokaryotic transcriptomics and proteomics of two strains of T. pyogenes with similar growth curves but different cytotoxicity. Studying the metabolic mechanisms of these differentially expressed genes and proteins can greatly promote the discovery of new biomarkers and improve the accuracy of biomarker identification, which is of great value for molecular mechanisms, biomarkers, early diagnosis of diseases, molecular typing, and prognosis. Our results indicate that the control of the virulence by tRNAs to bacteria during ribosome biosynthesis is crucial.

A plasmid-encoded inactive toxin-antitoxin system MtvT/MtvA regulates plasmid conjugative transfer and bacterial virulence in Pseudomonas aeruginosa

Plasmid-encoded toxin-antitoxin (TA) systems are known for their role in plasmid maintenance via post-segregational killing. Here, we identified an inactive type II TA system, MtvT/MtvA (MtvTA), encoded on the conjugative plasmid pPAD8 from the clinical Pseudomonas aeruginosa strain PAD8. Despite its annotation as a toxin, MtvT exhibited no detectable toxicity in our assays. Interestingly, the deletion of the MtvTA significantly increased the transfer efficiency of pPAD8 from PAD8 to P. aeruginosa strain PAO1. Functional assays revealed that the MtvTA complex negatively regulates plasmid transfer by binding to the promoters of dot/icm system genes. In addition, pPAD8ΔmtvTA attenuated the pathogenicity of the host strain compared to pPAD8, highlighting a regulatory role for MtvTA in virulence. Mechanistically, the MtvTA complex positively regulates the type III and type VI secretion systems and pyocyanin biosynthesis by directly binding to the promoters of exsA and rsmY/rsmZ and indirectly influencing lasI expression, respectively. These findings provide new insights into the regulatory roles of an inactive plasmid-encoded TA system, expanding our understanding of the interplay between plasmids and their bacterial hosts.

Multidrug resistance in Pseudomonas aeruginosa: genetic control mechanisms and therapeutic advances

Pseudomonas aeruginosa is a significant opportunistic pathogen, and its complex mechanisms of antibiotic resistance pose a challenge to modern medicine. This literature review explores the advancements made from 1979 to 2024 in understanding the regulatory networks of antibiotic resistance genes in Pseudomonas aeruginosa, with a particular focus on the molecular underpinnings of these resistance mechanisms. The review highlights four main pathways involved in drug resistance: reducing outer membrane permeability, enhancing active efflux systems, producing antibiotic-inactivating enzymes, and forming biofilms. These pathways are intricately regulated by a combination of genetic regulation, transcriptional regulators, two-component signal transduction, DNA methylation, and small RNA molecules. Through an in-depth analysis and synthesis of existing literature, we identify key regulatory elements mexT, ampR, and argR as potential targets for novel antimicrobial strategies. A profound understanding of the core control nodes of drug resistance offers a new perspective for therapeutic intervention, suggesting that modulating these elements could potentially reverse resistance and restore bacterial susceptibility to antibiotics. The review looks forward to future research directions, proposing the use of gene editing and systems biology to further understand resistance mechanisms and to develop effective antimicrobial strategies against Pseudomonas aeruginosa. This review is expected to provide innovative solutions to the problem of drug resistance in infectious diseases.

Protocol for examining the T3SS-mediated cytotoxicity of Pseudomonas aeruginosa using the A549 cell line

Pseudomonas aeruginosa utilizes a type III secretion system (T3SS) to directly inject effector proteins into host cells, leading to severe acute infections. Here, we present a protocol for detecting the T3SS-mediated cytotoxicity of P. aeruginosa using the A549 cell line. We describe the steps for the preparation of the A549 cell line and P. aeruginosa strains, cell seeding, bacterial culture, infection, and cytotoxicity assay. Additionally, we provide detailed procedures for data analysis. For complete details on the use and execution of this protocol, please refer to Huang et al.1.

The modification landscape of Pseudomonas aeruginosa tRNAs

RNA modifications have a substantial impact on tRNA function, with modifications in the anticodon loop contributing to translational fidelity and modifications in the tRNA core impacting structural stability. In bacteria, tRNA modifications are crucial for responding to stress and regulating the expression of virulence factors. Although tRNA modifications are well-characterized in a few model organisms, our knowledge of tRNA modifications in human pathogens, such as Pseudomonas aeruginosa, remains limited. Here, we leveraged two orthogonal approaches to build a reference landscape of tRNA modifications in Escherichia coli, which enabled us to identify similar modifications in P. aeruginosa Our analysis supports a substantial degree of conservation between the two organisms, while also uncovering potential sites of tRNA modification in P. aeruginosa tRNAs that are not present in E. coli The mutational signature at one of these sites, position 46 of tRNAGln1(UUG) is dependent on the P. aeruginosa homolog of TapT, the enzyme responsible for the 3-(3-amino-3-carboxypropyl) uridine (acp3U) modification. Identifying which modifications are present on different tRNAs will uncover the pathways impacted by the different tRNA-modifying enzymes, some of which play roles in determining virulence and pathogenicity.

Suppression of Pseudomonas aeruginosa type III secretion system by a novel calcium-responsive signaling pathway

Expression of the type III secretion system (T3SS) in Pseudomonas aeruginosa is exquisitely controlled by diverse environmental or host-related signals such as calcium (Ca2+), however, the signal transduction pathways remain largely elusive. In this study, we reported that FleR, the response regulator of the two-component system FleS/FleR, inhibits T3SS gene expression and virulence of P. aeruginosa uncoupled from its cognate histidine kinase FleS. Interestingly, FleR was found to repress T3SS gene expression under Ca2+-rich conditions independently of its DNA-binding domain. FleR activates the elevation of intracellular c-di-GMP contents and FleQ serves as the c-di-GMP effector to repress T3SS gene expression through the Gac/Rsm pathway. Remarkably, we found that AmrZ, a member of the FleR regulon, inhibits T3SS gene expression by directly targeting the promoter of exsCEBA in an expression level-dependent manner. This study revealed an intricate regulatory network that connects P. aeruginosa T3SS gene expression to the Ca2+ signal.

The modification landscape of P. aeruginosa tRNAs

RNA modifications have a substantial impact on tRNA function, with modifications in the anticodon loop contributing to translational fidelity and modifications in the tRNA core impacting structural stability. In bacteria, tRNA modifications are crucial for responding to stress and regulating the expression of virulence factors. Although tRNA modifications are well-characterized in a few model organisms, our knowledge of tRNA modifications in human pathogens, such as Pseudomonas aeruginosa, remains limited. Here we leveraged two orthogonal approaches to build a reference landscape of tRNA modifications in E. coli, which enabled us to identify similar modifications in P. aeruginosa. Our analysis revealed a substantial degree of conservation between the two organisms, while also uncovering potential sites of tRNA modification in P. aeruginosa tRNAs that are not present in E. coli. The mutational signature at one of these sites, position 46 of tRNAGln1(UUG) is dependent on the P. aeruginosa homolog of TapT, the enzyme responsible for the 3-(3-amino-3-carboxypropyl) uridine (acp3U) modification. Identifying which modifications are present on different tRNAs will uncover the pathways impacted by the different tRNA modifying enzymes, some of which play roles in determining virulence and pathogenicity.