Modulation of Virulence Factor Expression by Pathogen Target Cell Contact

Abstract

Upon contact with the eukaryotic cell, Yersinia pseudotuberculosis increased the rate of transcription of virulence genes ( yop ), as determined by in situ monitoring of light emission from individual bacteria expressing luciferase under the control of the yopE promoter. The microbe-host interaction triggered export of LcrQ, a negative regulator of Yop expression, via the Yop-type III secretion system. The intracellular concentration of LcrQ was thereby lowered, resulting in increased expression of Yops. These results suggest a key role for the type III secretion system of pathogenic bacteria to coordinate secretion with expression of virulence factors after physical contact with the target cell.