Project description:Gram-negative bacterial infections are causing increasing levels of morbidity due to the rise of resistance to established antibiotics. New antibiotic classes with distinct molecular mode of action are therefore required. Recently, a family of macrocyclic peptidomimetics was discovered that target the outer membrane LPS transport protein LptD to specifically inhibit bacterial growth in Pseudomonas spp. To characterize the interaction of these antibiotics with LptD from P. aeruginosa, we combined photo-crosslinkable peptidomimetics and hypothesis-free mass spectrometry-based proteomics. We provide evidence that the antibiotic cross-links to the periplasmic segment of LptD, containing a ß-jellyroll domain and an N-terminal insert domain that is characteristic of Pseudomonas spp. Binding of the antibiotic to the periplasmic segment of LptD is expected to block LPS transport, consistent with the proposed mode of action and observed specificity of these antibiotics. These insights may prove valuable for the discovery of new antibiotics targeting the LPS transport pathway in other Gram-negative bacteria.
Project description:Gram-negative bacterial infections are causing increasing levels of morbidity due to the rise of resistance to established antibiotics. New antibiotic classes with distinct molecular mode of action are therefore required. Recently, a family of macrocyclic peptidomimetics was discovered that target the outer membrane LPS transport protein LptD to specifically inhibit bacterial growth in Pseudomonas spp. To characterize the interaction of these antibiotics with LptD from P. aeruginosa, we combined photo-crosslinkable peptidomimetics and hypothesis-free mass spectrometry-based proteomics. We provide evidence that the antibiotic cross-links to the periplasmic segment of LptD, containing a ß-jellyroll domain and an N-terminal insert domain that is characteristic of Pseudomonas spp. Binding of the antibiotic to the periplasmic segment of LptD is expected to block LPS transport, consistent with the proposed mode of action and observed specificity of these antibiotics. These insights may prove valuable for the discovery of new antibiotics targeting the LPS transport pathway in other Gram-negative bacteria.
Project description:With the global increase in the use of carbapenems, several gram-negative bacteria have acquired carbapenem resistance, thereby limiting treatment options. Klebsiella pneumoniae is one of such notorious pathogen that is being widely studied to find novel resistance mechanisms and drug targets. These antibiotic-resistant clinical isolates generally harbor many genetic alterations, and identification of causal mutations will provide insights into the molecular mechanisms of antibiotic resistance. We propose a method to prioritize mutated genes responsible for antibiotic resistance, in which mutated genes that also show significant expression changes among their functionally coupled genes become more likely candidates. For network-based analyses, we developed a genome-scale co-functional network of K. pneumoniae genes, KlebNet (www.inetbio.org/klebnet). Using KlebNet, we could reconstruct functional modules for antibiotic-resistance, and virulence, and retrieved functional association between them. With complementation assays with top candidate genes, we could validate a gene for negative regulation of meropenem resistance and four genes for positive regulation of virulence in Galleria mellonella larvae. Therefore, our study demonstrated the feasibility of network-based identification of genes required for antimicrobial resistance and virulence of human pathogenic bacteria with genomic and transcriptomic profiles from antibiotic-resistant clinical isolates.
Project description:Natural products represent a rich source for antibiotics addressing versatile cellular targets. The deconvolution of their targets via chemical proteomics is often challenged by the introduction of large photocrosslinkers. Here we select elegaphenone, a largely uncharacterized natural product antibiotic bearing a native benzophenone core scaffold, for affinity-based protein profiling (AfBPP) in Gram-positive and Gram-negative bacteria. This study utilizes the alkynylated natural product scaffold as a probe to uncover intriguing biological interactions with the transcriptional regulator AlgP. Furthermore, proteome profiling of a Pseudomonas aeruginosa AlgP transposon mutant revealed unique insights into the mode of action. Elegaphenone enhanced the killing of intracellular P. aeruginosa in macrophages exposed to sub-inhibitory concentrations of the fluoroquinolone antibiotic norfloxacin.
Project description:Pseudomonas aeruginosa is an ubiquitous gram-negative bacterium that may colonize a wide range of organisms, including bacteria, plants, and animals. It is a human opportunistic pathogen which shows a great threat to immunocompromised patients. P. aeruginosa displays intrinsic resistance to many antibiotics, and has a high ability to develop novel mechanisms of resistance which forms a threat in hospital environments and makes it extremely hard to eradicate. Additionally over half of the genes of this bacteria have no described function, so it is urgent to search for proteins related to its pathogenicity and antibiotic resistance. The aim of this study was to characterise the P. aeruginosa PA2504 protein of unknown function. Basic phenotypic analysis did not indicate the role of PA2504 in the cell, thus, in order to recognize transcripts affected by the lack of PA2504 transcriptomes of the ΔPA2504 and the wild-type PAO1161 strains were compared using high-throughput RNA sequencing (RNA-seq). Using qRT-PCR method we determined that the level of PA2504 transcript is higher in the stationary phase of growth as compared to the exponential phase of bacterial growth (Log2 FC = 2,77) thus the samples for the RNA-seq experiments were withdrawn from this phase of growth.The RNA-seq revealed that the expression of 42 transcripts was changed in the ΔPA2504 mutant as compared to the parental PAO1161 strain and that the majority of them were connected to the sulphur transport/metabolism.
Project description:The spread of antimicrobial resistance (AMR), coupled with the decline in antibiotic development, has become a major public health concern. Recent studies estimate that around 700,000 people die each year from infections caused by multidrug-resistant (MDR) bacteria. This led the WHO to publish the ESKAPEE list of high priority pathogens for AMR, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli. Among these, Gram-negative bacteria (K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp., and E. coli) are particularly overrepresented. This is mainly due to their high propensity to develop multiple resistance mechanisms, in addition to their intrinsic resistance to many antimicrobials, which is due to their membrane composition and the expression of broad-spectrum efflux pumps. One strategy to combat such AMR is the use of drug enhancers that are able to restore the antibacterial activity of poorly active antibiotics. In this context, we demonstrated that the polyamino-isoprenyl enhancer, NV716, efficiently potentiates the antibacterial activity of two families of multi-target Ser/Cys-based enzyme inhibitors, namely the oxadiazolone derivatives (OX) and the Cyclipostins and Cyclophostin analogs (CyC), against Enterobacter cloacae, while remaining inactive against other Gram-negative bacteria. We confirmed that NV716 potentiates some OX & CyC compounds by permeabilizing the outer membrane and thus by increasing the inhibitor accumulation as shown by fluorescence confocal microscopy. By using bio-orthogonal click-chemistry activity-based protein profiling (CC-ABPP) approach coupled to proteomic analysis, we also identified the target proteins of the best OX & CyC inhibitors from E. cloacae lysate, thereby confirming their multi-target nature. Interestingly, 6 of the latter proteins were also captured via CC-ABPP in P. aeruginosa lysate, and are highly conserved in all Gram-negative bacteria. These results provide proof of concept that both OX & CyC, if successfully potentiated, could be used against a wide range of ESKAPEE Gram-negative bacteria.
Project description:Due to the rising incidence of antibiotic resistant infections, last-line antibiotics polymyxins have resurged in the clinics together with the appearance of new bacterial strategies of escape. The Gram-negative opportunistic pathogen Pseudomonas aeruginosa develops resistance to colistin/polymyxin by distinct molecular mechanisms, mostly involving the modification of the lipid A component of the LPS by proteins encoded within the arnBCDATEF-ugD (called arn) operon. We characterized a polymyxin-induced operon, named mipBA, present in P. aeruginosa group of strains devoid of the arn operon. Mass spectrometry-based quantitative proteomics showed that the absence of MipBA modifies the membrane proteome, notably impacting ParRS-regulated proteins, in response to polymyxin.
Project description:The race to combat antibiotic resistance and develop novel therapies has triggered studies on novel metal-based formulations. Silver remains a strong candidate since ancient times due to its multimodal and broad-spectrum activity against bacterial and fungal pathogens. N-heterocyclic carbene (NHC) complexes coordinate transition metals to generate a broad range of anticancer and/or antimicrobial agents with ongoing efforts being made to enhance lipophilicity and drug stability. The lead silver(I) acetate complex, 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*) (SBC3) synthesised by the Tacke group has previously demonstrated promising growth and biofilm-inhibiting properties. As an extension of this, we examined the responses of two structurally different bacteria to SBC3 using label-free quantitative proteomic analysis. Multidrug resistant Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) are associated with chronic wound infections and Cystic Fibrosis lung colonisation where co-infection often exacerbates disease. SBC3 increased the abundance of alginate biosynthesis, secretion system and drug detoxification proteins in P. aeruginosa whilst a multitude of pathways including anaerobic respiration, twitching motility, and ABC transport were decreased. This contrasted with affected pathways in S. aureus such as increased DNA replication/repair and cell redox homeostasis and decreased protein synthesis, lipoylation, glucose metabolism. Increased abundance of cell wall/membrane proteins were indicative of the structural damage induced by SBC3 to both cell types. These findings show the potential broad applications of SBC3 in treating Gram-positive and Gram-negative bacteria.
Project description:The development of new antibiotics against Gram-negative bacteria has to deal with the low permeability of the outer membrane. This obstacle can be overcome by utilizing siderophore-dependent iron uptake pathways as gates for antibiotic uptake. Iron-chelating siderophores are actively imported by bacteria, and their conjugation to antibiotics allows smuggling the latter into bacterial cells. Synthetic siderophore mimetics based on MECAM and DOTAM cores, both chelating iron via catechol groups, have been recently applied as versatile carriers of functional cargo. In the present study, we show that MECAM and the MECAM-ampicillin conjugate 3 transport iron into Pseudomonas aeruginosa cells via the catechol-type outer membrane transporters PfeA and PirA, and DOTAM solely via PirA. Differential proteomics and RTqPCR showed that MECAM import induced the expression of pfeA, whereas 3 led to an increase in the expression of pfeA and ampc, a gene conferring ampicillin resistance. The presence of DOTAM did not induce the expression of pirA, but upregulated the expression two zinc transporters (cntO and PA0781), pointing out that bacteria become zinc starved in the presence of this compound. Kinetic experiments with radioactive 55Fe demonstrated that iron uptake was as efficient as with the natural prototype siderophore enterobactin. The study provides a mechanistic and functional validation for DOTAM- and MECAM-based artificial siderophore mimetics as vehicles for the delivery of cargo into Gram-negative bacteria.