Project description:Bacterial pathogens causing systemic disease commonly evolve from organisms associated with localized infections but differ from their close relatives in their ability to overcome mucosal barriers by mechanisms that remain incompletely understood. Here we investigated whether acquisition of a regulatory gene, tviA, contributed to the ability of Salmonella enterica serotype Typhi to disseminate from the intestine to systemic sites of infection during typhoid fever. To study the consequences of acquiring a new regulator by horizontal gene transfer, tviA was introduced into the chromosome of S. enterica serotype Typhimurium, a closely related pathogen causing a localized gastrointestinal infection in immunocompetent individuals. Modulation of gene expression by TviA in serotype Typhi and Typhimurium was determined by profiling and found to be very comparable. Expression of flagellin, a pathogen associated molecular pattern (PAMP), was repressed by TviA when bacteria were grown at osmotic conditions encountered in tissue, but not at higher osmolarity present in the intestinal lumen. TviA-mediated flagellin repression enabled bacteria to evade sentinel functions of human model epithelia and resulted in increased bacterial dissemination to the spleen in a chicken model.
Project description:Secreted bacterial RNAs have recently emerged as a novel host-pathogen interaction mode. Naked RNA molecules are highly labile in the extracellular environment and must be protected by packaging into membrane vesicles or into complexes with RNA binding proteins. RNA secretion through membrane vesicles has been shown for several bacterial species but, surprisingly, proteins that bind and stabilize bacterial RNAs in the extracellular environment have not been reported yet. Here, we show that the bacterial pathogen L. monocytogenes secretes a small RNA binding protein that we named Zea. We show that Zea binds and stabilizes a subset of L. monocytogenes RNA, causing its accumulation in the extracellular medium. Zea modulates L. monocytogenes in vivo. Furthemore, Zea binds the mammalian non-self-RNA innate immunity sensor RIG-I and potentiates RIG-I-signaling during infection. This study provides a mechanism for the stability of extracellular RNA and unveils how secreted bacterial RNAs participate in the host-pathogen crosstalk.
Project description:Complete genome sequence of an Australian strain of Rouxiella badensis DAR84756 and resolution of the R. badensis DSM100043 and R. chamberiensis DSM28324 genomes