Project description:Yersinia pestis is a lethal pathogen responsible for millions of human deaths in three worldwide pandemics.The global acetylome analyses of Y. pestis grown under conditions mimicking two typical niches, i.e., the mammalian host (Mh) and the flea vector (Fv), were performed.
Project description:Yersinia pestis (Y. pestis) is the etiologic agent of the plague, an endemic zoonotic disease of critical clinical and historic importance. The species belongs to a genus comprising eleven members, three of which are human pathogens. Y. pestis and its closest extant relative, Yersinia pseudotuberculosis, are very similar in many respects, yet there is a distinct dichotomy between these species in terms of pathogenicity. Y. pseudotuberculosis produces a relatively benign food- or water-borne gastroenteritis with rare cases of potentially fatal bacteremia. In contrast, the characteristics of high infectivity and high mortality have made Y. pestis a pathogen of historic importance with devastating effects on the human populace over the course of three major pandemics. These qualities coupled with the emergence of multi-drug resistant variants make Y. pestis an ideal candidate for use as a bioterrorism agent. Consequentially, evolutionary biology of this organism has become a priority in the counter-terrorism research effort. The flow of genetic information within the Y. pseudotuberculosis/Y. pestis group motivated us to identify novel genes for the purpose of creating a pan-genome species DNA microarray to better understand the phylogenomic relationships among its members. Based on the sequence information be generated from the novel gene discovery project conducted at the PFGRC as well as other publicly available sources regarding Yersinia spp. genome sequences, we designed a species microarray which represents the hitherto known genetic repertoire of this taxonomic group. In order to create a species microarray that represents novel genes or genes with significant sequence variation, the ArrayOligoSelector software (http://arrayoligosel.sourceforge.net/) was used to design a 70-mer oligonucleotide for each of the annotated ORFs or partial ORFs. A detailed description of the 70-mer oligo design process and filters developed by the PFGRC can be found on the PFGRC web site at (http://pfgrc.tigr.org/presentations/seminars/oligo_design_final.pdf).
Project description:Granulomas are organized immune cell aggregates formed in response to chronic infection or antigen persistence. The bacterial pathogen Yersinia pseudotuberculosis (Yp) blocks innate inflammatory signalling and immune defence, inducing neutrophil-rich pyogranulomas (PGs) within lymphoid tissues. Here we uncover that Yp also triggers PG formation within the murine intestinal mucosa. Mice lacking circulating monocytes fail to form defined PGs, have defects in neutrophil activation and succumb to Yp infection. Yersinia lacking virulence factors that target actin polymerization to block phagocytosis and reactive oxygen burst do not induce PGs, indicating that intestinal PGs form in response to Yp disruption of cytoskeletal dynamics. Notably, mutation of the virulence factor YopH restores PG formation and control of Yp in mice lacking circulating monocytes, demonstrating that monocytes override YopH-dependent blockade of innate immune defence. This work reveals an unappreciated site of Yersinia intestinal invasion and defines host and pathogen drivers of intestinal granuloma formation.
Project description:RNA degradation is an essential process that allows bacteria to regulate gene expression and has emerged as an important mechanism for controlling virulence. However, the individual contributions of RNases in this process are mostly unknown. Here, we report that of 11 tested potential RNases of the intestinal pathogen Yersinia pseudotuberculosis, two, the endoribonuclease RNase III and the exoribonuclease PNPase, repress the synthesis of the master virulence regulator LcrF. LcrF activates the expression of virulence plasmid genes encoding the type III secretion system (Ysc-T3SS) and its substrates (Yop proteins), that are employed to inhibit immune cell functions during infection. Loss of both RNases led to an increase in lcrF mRNA levels and stability. Our work indicates that PNPase exerts its influence through YopD, known to accelerate lcrF mRNA degradation. Loss of RNase III results in the downregulation of the CsrB and CsrC RNAs, leading to increased availability of active CsrA, which has previously been shown to enhance lcrF mRNA translation and stability. Other factors that influence the translation process and were found to be differentially expressed in the RNase III-deficient mutant could support this process. Transcriptomic profiling further revealed that Ysc-T3SS-mediated Yop secretion leads to global reprogramming of the Yersinia transcriptome with a massive shift of the expression from chromosomal towards virulence plasmid-encoded genes. A similar extensive transcriptional reprogramming was also observed in the RNase III-deficient mutant under non-secretion conditions. This illustrated that RNase III enables immediate coordination of virulence traits, such as Ysc-T3SS/Yops, with other functions required for host-pathogen interactions and survival in the host.
Project description:Salmonella enterica represent a major disease burden worldwide. While non-typhoidal Salmonella (NTS) serovars trigger self-limiting diarrhoea, leading to occasional secondary bacteraemia, S. enterica serovar Typhi is responsible for potentially life-threatening Typhoid fever. Dendritic cells (DCs) are key professional antigen presenting cells of the human immune system. The ability of pathogenic bacteria to subvert DC functions and prevent T cell recognition contributes to their survival and dissemination within the host. Here, we adapted Dual RNA-sequencing to define how different Salmonella pathovariants remodel their gene expression in tandem with that of infected DCs. We find DCs harness iron handling pathways to defend against invading Salmonellas, which, the human pathogen S. Typhi is able to circumvent. We show that S. Typhi mounts a robust response to host oxidative stress to avoid host iron-mediated defence mechanisms. In parallel, we provide evidence that invasive non-typhoidal Salmonella employs several strategies to impair DC functions and undertake alternative nutrient scavenging strategies to survive in the hostile intracellular environment.
Project description:A temporal multi-omic analysis of Y. pestis and Y. pseudotuberculosis at physiologically relevant temperatures was performed to gain insights into how an acute and highly lethal bacterial pathogen, Y. pestis, differs from its less virulent progenitor, Y. pseudotuberculosis. Associated transcriptomics data have been deposited in GEO under accession number GSE30634.