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: The goal of this study was to use RNA-seq to define the Klebsiella pneumoniae transcriptome recorded under 5 different experimental conditions, and to identify signature genes of each condition by comparing global transcriptional profiles. Methods: mRNA profiles were generated for Klebsiella pneumoniae CH1034 clinical isolate, in triplicate, by deep sequencing. Total RNAs were harvested from bacteria cultured at 37°C in M63B1 minimal media under different conditions: (i) planktonic aerobic condition at OD 620nm=0.250 (exponential growth-phase), (ii) overnight planktonic aerobic condition (stationnary growth-phase), (iii) biofilm in a flow-cell chamber after 7 hours of incubation (7-hours old biofilm), (iv) biofilm in a flow-cell chamber after 13 hours of incubation (13-hours old biofilm), (v) bacteria self-dispersed from biofilm recovered in the flow-cell effluent (biofilm-dispersed bacteria). Ribosomal RNAs were removed using the Bacteria Ribo-Zero Magnetic kit (Epicentre Biotechnologies). Libraries were prepared using the TruSeq Stranded mRNA Sample Preparation kit (Illumina), and 50bp single-reads were obtained by HiSeq 2000 (Illumina).The sequence reads that passed FastQC quality filters were mapped to the CH1034 genome using BurrowsâWheeler Aligner (BWA) (0.7.12-r1039 version). The transcript levels were determined using HTSeq-count (0.6.1p1 version) with union mode followed by DESeq (1.16.0 version) analysis. qRTâPCR validation was performed using SYBR Green assays. Results: We found that each condition has a specific transcriptional profile, and we identify 4 robust signature genes for each. Conclusion: Our study represents the first detailed analysis of K. pneumoniae transcriptomes under different experimental conditions generated by RNA-seq technology. The data reported here should permit the dissection of complex biologic functions involved in the transition between the sessile and planktonic modes of growth. Determination of the transcriptional profiling of Klebsiella pneumoniae under 5 different experimental conditions. mRNA profiles were generated for bacteria under exponential planktonic growth-phase, stationary planktonic growth-phase, 7 hours-old biofilm, 13 hours-old biofilm and biofilm-dispersed modes, each in three biological replicates, by deep sequencing using Illumina HiSeq
Project description:To investigate the whole-genome gene expression difference between the wild-type and capsule deletion mutant in Klebsiella pneumoniae MGH 78578. The mutants analyzed in this study are further described in Huang T.W., Stapleton J.C., Chang H.Y., Tsai S.F., Palsson B.O., Charusanti P. Capsule removal via lambda-Red knockout system perturbs biofilm formation and fimbriae extression in Klesiella pneumoniae MGH 78578 (manuscript submission) A six chip study using total RNA recovered from three separate wild-type cultures and three separate cultures of a capsule deltion mutant of Klebsiella pneumoniae MGH 78578. The capsule gene cluster (KPN_02493 to KPN_02515) was entirely removed in the capsule deletion mutant. Each chip measures the expression level of 5,305 genes from Klebsiella pneumoniae MGH 78578 and the associated five plasmids (pKPN3, pKPN4, pKPN5, pKPN6 and pKPN7) with 50-mer oligo tiling array with 30-mer spacer.
Project description:To investigate the whole-genome gene expression difference between the wild-type and capsule deletion mutant in Klebsiella pneumoniae MGH 78578. The mutants analyzed in this study are further described in Huang T.W., Stapleton J.C., Chang H.Y., Tsai S.F., Palsson B.O., Charusanti P. Capsule removal via lambda-Red knockout system perturbs biofilm formation and fimbriae extression in Klesiella pneumoniae MGH 78578 (manuscript submission)
Project description:The inappropriate use of antibiotics is a severe public health problem worldwide, contributing to the emergence of multidrug-resistant (MDR) bacteria. To explore the possible impacts of the inappropriate use of antibiotics on the immune system, we use Klebsiella pneumoniae (K. pneumoniae) infection as an example and show that imipenem increases the mortality of mice infected by MDR K. pneumoniae. Further studies demonstrate that imipenem enhances the secretion of outer membrane vesicles (OMVs) with significantly elevated presentation of GroEL, which promotes the phagocytosis of OMVs by macrophages that depends on the interaction between GroEL and its receptor LOX-1. OMVs cause the pyroptosis of macrophages and the release of proinflammatory cytokines, which contribute to exacerbated inflammatory responses. We propose that the inappropriate use of antibiotics in the cases of infection by MDR bacteria such as K. pneumoniae might cause damaging inflammatory responses, which underlines the pernicious effects of inappropriate use of antibiotic.
Project description:Purpose: The goal of this study was to use RNA-seq to define the Klebsiella pneumoniae transcriptome recorded under 5 different experimental conditions, and to identify signature genes of each condition by comparing global transcriptional profiles. Methods: mRNA profiles were generated for Klebsiella pneumoniae CH1034 clinical isolate, in triplicate, by deep sequencing. Total RNAs were harvested from bacteria cultured at 37°C in M63B1 minimal media under different conditions: (i) planktonic aerobic condition at OD 620nm=0.250 (exponential growth-phase), (ii) overnight planktonic aerobic condition (stationnary growth-phase), (iii) biofilm in a flow-cell chamber after 7 hours of incubation (7-hours old biofilm), (iv) biofilm in a flow-cell chamber after 13 hours of incubation (13-hours old biofilm), (v) bacteria self-dispersed from biofilm recovered in the flow-cell effluent (biofilm-dispersed bacteria). Ribosomal RNAs were removed using the Bacteria Ribo-Zero Magnetic kit (Epicentre Biotechnologies). Libraries were prepared using the TruSeq Stranded mRNA Sample Preparation kit (Illumina), and 50bp single-reads were obtained by HiSeq 2000 (Illumina).The sequence reads that passed FastQC quality filters were mapped to the CH1034 genome using Burrows–Wheeler Aligner (BWA) (0.7.12-r1039 version). The transcript levels were determined using HTSeq-count (0.6.1p1 version) with union mode followed by DESeq (1.16.0 version) analysis. qRT–PCR validation was performed using SYBR Green assays. Results: We found that each condition has a specific transcriptional profile, and we identify 4 robust signature genes for each. Conclusion: Our study represents the first detailed analysis of K. pneumoniae transcriptomes under different experimental conditions generated by RNA-seq technology. The data reported here should permit the dissection of complex biologic functions involved in the transition between the sessile and planktonic modes of growth.
Project description:Polymyxins are increasingly used as the critical last-resort therapeutic options for multidrug-resistant gram-negative bacteria. Unfortunately, polymyxin resistance has increased gradually for the last few years. Although studies on mechanisms of polymyxin are expanding, system-wide analyses of the underlying mechanism for polymyxin resistance and stress response are still lacking. To understand how Klebsiella pneumoniae adapt to colistin (polymyxin E) pressure, we carried out proteomic analysis of Klebsiella pneumoniae strain cultured with different concentrations of colistin. Our results showed that the proteomic responses to colistin treatment in Klebsiella pneumoniae involving several pathways, including (i) gluconeogenesis and TCA cycle; (ii) arginine biosynthesis; (iii) porphyrin and chlorophyll metabolism; and (iv) enterobactin biosynthesis. Interestingly, decreased abundance of class A β-lactamases including TEM, SHV-11, SHV-4 were observed in cells treated with colistin. Moreover, we also present comprehensive proteome atlases of paired polymyxin-susceptible and -resistant Klebsiella pneumoniae strains. The polymyxin-resistant strain Ci, a mutant of Klebsiella pneumoniae ATCC BAA 2146, showed missense mutation in crrB. The crrB mutant Ci, which displayed lipid A modification with 4-amino-4-deoxy-L-arabinose (L-Ara4N) and palmitoylation, showed striking increases of CrrAB, PmrAB, PhoPQ, ArnBCADT and PagP. We hypothesize that crrB mutations induce elevated expression of the arnBCADTEF operon and pagP via PmrAB and PhoPQ. Moreover, multidrug efflux pump KexD, which was induced by crrB mutation, also contributed to colistin resistance. Overall, our results demonstrated proteomic responses to colistin treatment and the mechanism of CrrB-mediate colistin resistance, which may further offer valuable information to manage polymyxin resistance.
Project description:Exploiting genomic differences between Listeria monocytogenes EGDe isolates reveals crucial roles for SigB and wall rhamnosylation in biofilm formation.
Project description:The SaeRS two-component regulatory system of Staphylococcus aureus is known to affect the expression of many genes. The SaeS protein is the histidine kinase responsible for phosphorylation of the response regulator SaeR. In S. aureus Newman, the sae system is constitutively expressed due to a point mutation in saeS, relative to other S. aureus strains, which results in substitution of proline for leucine at amino acid 18. Strain Newman is unable to form a robust biofilm and we report here that the biofilm-deficient phenotype is due to the saeSP allele. Replacement of the Newman saeSP with saeSL, or deletion of saeRS, resulted in a biofilm-proficient phenotype. Newman culture supernatants were observed to inhibit biofilm formation by other S. aureus strains, but did not affect biofilm formation by S. epidermidis. Culture supernatants of Newman saeSL or Newman ΔsaeRS had no significant effect on biofilm formation. The inhibitory factor was inactivated by incubation with proteinase K, but survived heating, indicating that the inhibitory protein is heat-stable. The inhibitory protein was found to affect the attachment step in biofilm formation, but had no effect on preformed biofilms. Replacement of saeSL with saeSP in the biofilm-proficient S. aureus USA300 FPR3757 resulted in the loss of biofilm formation. Culture supernatants of USA300 FPR3757 saeSP, did not inhibit biofilm formation by other staphylococci, suggesting that the inhibitory factor is produced but not secreted in the mutant strain. A number of biochemical methods were utilized to isolate the inhibitory protein. Although a number of candidate proteins were identified, none were found to be the actual inhibitor. In an effort to reduce the number of potential inhibitory genes, RNA-Seq analyses were done with wild-type strain Newman and the saeSL and ΔsaeRS mutants. RNA-Seq results indicated that sae regulates many genes that may affect biofilm formation by Newman.