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RmpA as a Global Regulator Modulates Switching Between Hypermucoviscosity and Biofilm in Hypervirulent Klebsiella pneumoniae [ChIP-seq]

ABSTRACT: Hypervirulent Klebsiella pneumoniae (hvKp) is a significant pathogen causing severe community-acquired infections, characterized by the presence of a virulence plasmid. The plasmid-encoded regulator of mucoid phenotype A (RmpA) activates the expression of capsule genes, resulting in a hypermucoviscosity phenotype strongly associated with increased virulence. RmpA features a LuxR DNA-binding domain and a signaling-responsive domain, typical of proteins that regulate multiple biological processes. However, the comprehensive regulatory mechanisms of RmpA in hvKp remain unclear. Herein, RNA-seq showed that RmpA activates carbohydrate metabolism pathways while repressing those related to DNA replication, ribosome metabolism, and biofilm formation. ChIP-seq further confirmed RmpA’s role as a global regulator that not only enhances capsule production by activating transcripts within the capsule locus, but also upregulates the expression of key genes involved in synthesizing capsule precursors. RmpA regulates the phenotypic switch between hypermucoviscosity and biofilm formation by repressing type III fimbriae genes. In addition, Expression of RmpA in Escherichia coli induced global transcriptional changes, suggesting it functions as a global regulator across species. These findings position RmpA as a central regulator in hvKp, orchestrating metabolic pathways and phenotypic traits essential for virulence.

ORGANISM(S): Klebsiella pneumoniae

PROVIDER: GSE286111 | GEO | 2025/01/14

REPOSITORIES: GEO

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Project description:The emergence of hypervirulent Klebsiella pneumoniae (hvKP) strains poses a significant threat to public health due to their high mortality rates and propensity to cause severe community-acquired infections in otherwise healthy individuals. The ability of hvKP to form biofilms and produce a protective capsule contributes to its enhanced virulence and is a significant challenge to effective antibiotic treatment. Therefore, understanding the molecular mechanisms underlying hvKP virulence and biofilm formation is crucial for developing new therapeutic strategies. Polyphosphate Kinase 1 (PPK1) is an enzyme responsible for inorganic polyphosphate synthesis and plays a vital role in regulating various physiological processes in bacteria. In this study, we investigated the impact of polyP metabolism on the biofilm and capsule formation and virulence traits in hvKP using Dictyostelium discoideum amoeba as a model host. We found that the PPK1 null-mutant was impaired in biofilm and capsule formation and showed attenuated virulence in D. discoideum compared to the wild-type strain. We performed a shotgun proteomic analysis of the PPK1 mutant and wild-type strain to gain further insight into the underlying molecular mechanism. The results revealed that the PPK1 mutant had a differential expression of proteins (DEP) involved in capsule synthesis (Wzi - Ugd), biofilm formation (MrkC-D-H), synthesis of the colibactin genotoxin precursor (ClbB), as well as proteins associated with the synthesis and modification of lipid A (ArnB -LpxC - PagP). These proteomic findings corroborate the phenotypic observations and indicate that the PPK1 mutation is associated with impaired biofilm and capsule formation and attenuated virulence in hypervirulent K. pneumoniae. Overall, our study highlights the importance of polyP synthesis in regulating extracellular biomolecules and virulence in K. pneumoniae and provides insights into potential therapeutic targets for treating K. pneumoniae infections.

Project description:Purpose:Investigated transcriptome profile changes in the lungs of infected mice at different time points, to increase our understanding of hvKp pulmonary infection and to screen for genes or targets of research value. microarray and quantitative reverse transcription polymerase chain reaction (qRT–PCR) methods and to evaluate protocols for optimal high-throughput data analysis Methods: Animals were randomly divided into four infection groups and one control group (five mice per group), and the infected mice were euthanized at 12, 24, 48 and 60 h post-infection (hpi), respectively, while the control group mice were euthanized immediately after delivery of PBS at the 0 h time point. The lungs of the mice were isolated and divided into two parts for subsequent histopathologic examination or total RNA extraction. Results: Using the control group (0 hpi) as a reference, 6247 DEGs were identified across four time points after hvKp infection. At 12 hpi, 939 upregulated DEGs and 439 downregulated DEGs were detected, and by 60 hpi, 2647 upregulated DEGs and 2806 downregulated DEGs were detected. Overall, the number of upregulated and downregulated DEGs increased over time and a total of 688 genes were upregulated and 240 genes downregulated in common for all time points. And 12 of these were validated with qRT–PCR. RNA-seq data had a linear relationship with qRT–PCR for more than four orders of magnitude and a goodness of fit (R2) of 0.9548. To get a more holistic view, DEGs were clustered into nine clusters according to their temporal expression patterns.WGCNA was performed with the detected DEGs. The dynamic tree cutting algorithm in the WGCNA package was used to process the hierarchical clustering tree, and a total of 28 different modules were finally obtained. Conclusions: Our work both validates the results of previous studies on K. pneumoniae pulmonary infections and provides new additions and insights on hvKp pulmonary infections, which may contribute to the development of therapeutic approaches to reduce hvKp lung inflammation.

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RmpA as a Global Regulator Modulates Switching Between Hypermucoviscosity and Biofilm in Hypervirulent Klebsiella pneumoniae [ChIP-seq]

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