Bacteria
Salmonella Effectors SseK1 and SseK3 Target Death Domain Proteins in the TNF and TRAIL Signaling Pathways*Many Gram-negative pathogens employ type three secretion systems to translocate specialised bacterial effector proteins into the host cell. Endogenous levels of arginine-GlcNAcylation by two Salmonella effectors, SseK1 and SseK3, were determined by quantitative MS-based proteomics. The effectors modified different host death domain containing signaling proteins required for inflammatory and cell death signaling. The study developed new tools to study host-effector interactions and established the importance of native levels of effector expression in distinguishing between authentic and misleading interactions and activities.
Virulence Factors Produced by Staphylococcus aureus Biofilms Have a Moonlighting Function Contributing to Biofilm IntegrityWe comprehensively profiled intracellular and ECM proteomes of S. aureus flow biofilms and complemented these data by metabolic footprint analysis and phenotypic assays. We show that moonlighting, secreted virulence factors and ribosomal proteins within the ECM contribute to biofilm stabilization. Mechanistically, we propose that these alkaline proteins get protonated in an acidified ECM (because of the release of acids upon fermentation) mediating electrostatic interactions with anionic cell surface components, eDNA, and metabolites, which leads to cell aggregation and ECM stabilization.
Metabolic Cross-talk Between Human Bronchial Epithelial Cells and Internalized Staphylococcus aureus as a Driver for InfectionStaphylococcus aureus invades bronchial epithelial cells to reach underlying lung tissue and to escape from the human immune defenses or antibiotic therapy. The internalized pathogen achieves these objectives by differentiation into growing and dormant subpopulations. Here we tracked the dynamic interactions between internalized bacteria and their host over four days by quantitative proteomics. The results highlight metabolic cross-talk between host and pathogen as a key driver for mutual adaptation and the outcome of infection.
Investigating Lactococcus lactis MG1363 Response to Phage p2 Infection at the Proteome LevelThe cellular response of Lactococcus lactis MG1363 to infection by the virulent phage p2 was characterized through label-free quantitative proteomics. Combined with a targeted approach, we identified the highest proteome coverage for phage p2, a model for the most predominant group of lactococcal phages in the dairy industry worldwide. Four bacterial gene candidates possibly involved in phage infection were disrupted through specific knockouts to investigate their importance. Deletion of gene llmg_0219 (unknown function) resulted in a resistance to phage p2.
Proteomics Reveals Multiple Phenotypes Associated with N-linked Glycosylation in Campylobacter jejuniN-linked protein glycosylation (Pgl) in Campylobacter jejuni is required for chicken colonization and human virulence, yet its biological role remains unknown. pgl gene deletion resulted in a significant rearrangement of the C. jejuni proteome that leads to alterations in crucial phenotypes including stress response, nutrient uptake, electron transport and chemotaxis, and is essential for full activity of the Nap nitrate reductase. N-glycosylation therefore contributes to multiple “virulence” phenotypes in C. jejuni.
Decreased Antibiotic Susceptibility Driven by Global Remodeling of the Klebsiella pneumoniae ProteomeKeasey et al. investigate the proteomic mechanisms used to circumvent the effect of antibiotics by Gram-negative bacteria that do not harbor traditional genetic elements of resistance. The proteomes of Klebsiella pneumoniae bacteria that survived treatment with antibiotic inhibitors of ribosomal protein synthesis were examined by label-free quantitative mass spectrometry. Taking a systems approach, they identify both common and drug-specific molecular pathways that facilitate decreased susceptibility to antibiotics. These results explain why some antibiotic treatments fail even with sensitive pathogens.
Secretome Dynamics in a Gram-Positive Bacterial ModelTsolis et al., reveal that the regulation of protein secretion in a Gram positive bacterial model is complex. Some of this regulation is transcriptional but a lot occurs post-transcriptionally and affects different exported proteins in different ways. Main Sec and chaperone machineries are not part of this regulation.
Quantitative Proteomics of the 2016 WHO Neisseria gonorrhoeae Reference Strains Surveys Vaccine Candidates and Antimicrobial Resistance DeterminantsWe present the first large-scale quantitative MS-based profiling of cell envelopes and cytoplasmic proteins derived from a diverse panel of WHO gonococcal reference strains possessing all existing AMR profiles and intended for quality assurance in laboratory investigations. We describe nine novel gonorrhea vaccine candidates and six potential global proteomic AMR markers. A reference proteomics databank for gonococcal vaccine and AMR research endeavors is provided, which enables microbiological, clinical, or epidemiological projects and enhances the utility of the WHO reference strains.
A New Tool to Reveal Bacterial Signaling Mechanisms in Antibiotic Treatment and ResistanceChanges in proteome and phosphoproteome have been determined in E. coli treated with the antibiotics colistin or ciprofloxacin and in a bona-fide mcr-1 positive colistin resistant strain. The results reveal extensive phosphorylation on bacterial proteins and motif specific phosphorylation changes during resistance development. Moreover, regulated sites show high evolutionary conservation, indicating an important biological role. Together, this indicates that phosphorylation mediated signaling could be used as a specific target for drug design.