Modulation of a thermoregulated type VI secretion system by AHL-dependent Quorum Sensing in Yersinia pseudotuberculosis
The type VI secretion system (T6SS) is a novel secretion system found in many Gram-negative bacterial pathogens, which appears to be tightly regulated by different regulatory mechanisms. In the present study, we identified 4 T6SS clusters in Yersinia pseudotuberculosis and demonstrated that they were differentially thermoregulated. Among them, T6SS4 was preferentially expressed at 26°C, and its expression was growth phase dependent and subject to quorum sensing regulation. Both YpsI and YtbI AHL synthases contributed to the positive regulation of T6SS4, whereas YpsI synthase played the major role as T6SS4 expression was reduced strongly in the ypsI mutant strain but weakly in the ytbI mutant strain. Moreover, we provided evidence that exogenous addition of different synthetic AHLs complemented T6SS4 expression in different efficiencies in an ypsIytbI double mutant strain, suggesting C6-HSL had an antagonistic effect on T6SS4 expression. This is the first study demonstrating that the expression of T6SS is precisely regulated by temperature, growth phase, and AHL-dependent quorum sensing systems in Y. pseudotuberculosis.
KeywordsYersinia pseudotuberculosis Type VI secretion system Quorum sensing N-acylhomoserine lactones
We are indebted to Paul Williams, Miguel Cámara, and Steve Atkinson, at the University of Nottingham, for their technical assistance and for providing valuable reagents. We thank Stephen C. Winans at Cornell University for kindly providing AHL signal molecular producer E. coli DH5α(pJZ365). We would also like to thank Dr. Simon Rayner for helpful comments and suggestions. This work was funded by grants from the National Natural Science Foundation of China (Grants No. 30570020 and 30770026).
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