Abounding use of cobalt oxide nanoparticles (Co3O4) requires a detailed understanding of their environmental and biomedical nanotoxicity and an eminent solution to the associated hazards; molecular and atomic aspects of...
An essential feature of the pathogenesis of Salmonella enterica serovar Enteritidis (S. Enteritidis; wild type (WT)) is its ability to survive in diverse micro-environmental stress conditions such as encountering antimicrobial peptides (AMPs), glucose and micronutrient starvation. These stress factors trigger virulence genes encoded on Salmonella pathogenicity islands (SPIs) and determine the efficiency of enteric infection. Although oligosaccharide/oligonucleotide binding-fold (OB-fold) family of protein has been identified as an important stress response and virulence determinant, functional information on members of this family is currently limited. In this study, we decipher the role of YdeI that belongs to OB-fold family of proteins in stress response and virulence of S. Enteritidis. When ydeI was deleted, ΔydeI showed reduced survival during AMPs, glucose, and Mg2+ starvation stress compared to WT. GFP reporter and quantitative real time (qRT)-PCR assays showed ydeI was transcriptionally regulated by PhoP, which is a major regulator of stress and virulence. Further, ΔydeI displayed ~89% reduced invasion into HCT116 cells, ~15-fold reduced intra-macrophage survival, and downregulation of several SPI-1 and SPI-2 genes encoding the type three secretion system apparatus and effector proteins. The mutant showed attenuated virulence compared to WT, confirmed by its reduced bacterial counts in feces, mLN, spleen and liver of C57BL/6 mice. qRT-PCR analyses of ΔydeI displayed differential expression of 45 PhoP-regulated genes, which were majorly involved in metabolism, transport, membrane remodeling, and drug resistance in different stress conditions. YdeI is, therefore, an important protein that modulates S. Enteritidis virulence and adaptation to stress during infection. IMPORTANCE: S. Enteritidis during its lifecycle encounters diverse stress factors inside host. These intracellular conditions allow activation of specialized secretion systems to cause infection. We report a conserved membrane protein YdeI and elucidate its role in protection to various intracellular stress conditions. A key aspect of the study of pathogens stress response mechanism is its clinical relevance during host-pathogen interaction. Bacterial adaptation to stress plays a vital role in evolution of pathogens resistance to therapeutic agents. Therefore, investigation of the role of YdeI is vital for understanding the molecular basis of regulation of Salmonella pathogenesis. In conclusion, our findings may contribute to finding potential targets to develop new intervention strategies for treatment and prevention of enteric diseases.
The frequency of Candida infections is currently rising, and thus adversely impacting global health. The situation is exacerbated by azole resistance developed by fungal pathogens. Candida tropicalis is an opportunistic pathogen that causes candidiasis, for example, in immune-compromised individuals, cancer patients, and those who undergo organ transplantation. It is a member of the non-albicans group of Candida that are known to be azole-resistant, and is frequently seen in individuals being treated for cancers, HIV-infection, and those who underwent bone marrow transplantation. Although the genome of C. tropicalis was sequenced in 2009, the genome annotation has not been supported by experimental validation. In the present study, we have carried out proteomics profiling of C. tropicalis using high-resolution Fourier transform mass spectrometry. We identified 2743 proteins, thus mapping nearly 44% of the computationally predicted protein-coding genes with peptide level evidence. In addition to identifying 2591 proteins in the cell lysate of this yeast, we also analyzed the proteome of the conditioned media of C. tropicalis culture and identified several unique secreted proteins among a total of 780 proteins. By subjecting the mass spectrometry data derived from cell lysate and conditioned media to proteogenomic analysis, we identified 86 novel genes, 12 novel exons, and corrected 49 computationally-predicted gene models. To our knowledge, this is the first high-throughput proteomics study of C. tropicalis validating predicted protein coding genes and refining the current genome annotation. The findings may prove useful in future global health efforts to fight against Candida infections.
BackgroundSalmonella enterica serovar Enteritidis, the most common cause of human gastroenteritis, employs several virulence factors including lipopolysaccharide (LPS) for infection and establishment of disease inside the host. The LPS of S. enterica serovar Enteritidis consists of lipid A, core oligosaccharide and O-antigen (OAg). The OAg consists of repeating units containing different sugars. The sugars of OAg are synthesized and assembled by a set of enzymes encoded by genes organized into clusters. Present study focuses on the effect of deletion of genes involved in biosynthesis of OAg repeating units on resistance to antimicrobial peptides and virulence in mice.MethodsIn the present study, the OAg biosynthesis was impaired by deleting tyv, prt and wbaV genes involved in tyvelose biosynthesis and its transfer to OAg. The virulence phenotype of resulting mutants was evaluated by assessing resistance to antimicrobial peptides, serum complement, adhesion, invasion and in vivo colonization.ResultsDeletion of the above three genes resulted in the production of OAg-negative LPS. All the OAg-negative mutants showed phenotype reported for rough strains. Interestingly, ΔwbaV mutant showed increased resistance against antimicrobial peptides and normal human serum. In addition, the ΔwbaV mutant also showed increased adhesion and invasion as compared to the other two O-Ag negative mutants Δtyv and Δprt. In vivo experiments also confirmed the increased virulent phenotype of ΔwbaV mutant as compared to Δprt mutant.ConclusionOAg-negative mutants are known to be avirulent; however, this study demonstrates that certain OAg negative mutants e.g. ∆wbaV may also show resistance to antimicrobial peptides and cause colitis in Streptomyces pretreated mouse model.
Salmonella Enteritidis causes food-borne gastroenteritis by the two type three secretion systems (TTSS). TTSS-1 mediates invasion through intestinal lining, and TTSS-2 facilitates phagocytic survival. The pathogens' ability to infect effectively under TTSS-1-deficient background in host's phagocytes is poorly understood. Therefore, pathobiological understanding of TTSS-1-defective nontyphoidal Salmonellosis is highly important. We performed a comparative global proteomic analysis of the isogenic TTSS-1 mutant of Salmonella Enteritidis (M1511) and its wild-type isolate P125109. Our results showed 43 proteins were differentially expressed. Functional annotation further revealed that differentially expressed proteins belong to pathogenesis, tRNA and ncRNA metabolic processes. Three proteins, tryptophan subunit alpha chain, citrate lyase subunit alpha, and hypothetical protein 3202, were selected for in vitro analysis based on their functional annotations. Deletion mutants generated for the above proteins in the M1511 strain showed reduced intracellular survival inside macrophages in vitro. In sum, this study provides mass spectrometry-based evidence for seven hypothetical proteins, which will be subject of future investigations. Our study identifies proteins influencing virulence of Salmonella in the host. The study complements and further strengthens previously published research on proteins involved in enteropathogenesis of Salmonella and extends their role in noninvasive Salmonellosis.
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