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YplA Is Exported by the Ysc, Ysa, and Flagellar Type III Secretion Systems of Yersinia enterocolitica. Briana M. Young, 2002.Yersinia enterocolitica maintains three different pathways for type III protein secretion . Each pathway requires the activity of a specific multicomponent apparatus or type III secretion system (TTSS) . Two of the TTSSs are categorized as contact-dependent systems which have been shown in a number of different symbiotic and pathogenic bacteria to influence interactions with host organisms by targeting effector proteins into the cytosol of eukaryotic cells . The third TTSS is required for the assembly of flagella and the secretion of the phospholipase YplA, which has been implicated in Y . enterocolitica virulence . In this study, YplA was expressed from a constitutive promoter in strains that contained only a single TTSS . It was determined that each of the three TTSSs is individually sufficient for YplA secretion . Environmental factors such as temperature, calcium availability, and sodium chloride concentration affected the contribution of each system to extracellular protein secretion and, under some conditions, more than one TTSS appeared to operate simultaneously . This suggests that some proteins might normally be exported by more than one TTSS in Y . enterocolitca . Role for Salmonella enterica Enterobacterial Common Antigen in Bile Resistance and Virulence. Francisco Ramos-Morales, 2003.Passage through the digestive tract exposes Salmonella enterica to high concentrations of bile salts, powerful detergents that disrupt biological membranes . Mutations in the wecD or wecA gene, both of which are involved in the synthesis of enterobacterial common antigen (ECA), render S . enterica serovar Typhimurium sensitive to the bile salt deoxycholate . Competitive infectivity analysis of wecD and wecA mutants in the mouse model indicates that ECA is an important virulence factor for oral infection . In contrast, lack of ECA causes only a slight decrease in Salmonella virulence during intraperitoneal infection . A tentative interpretation is that ECA may contribute to Salmonella virulence by protecting the pathogen from bile salts .
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