INVESTIGATING TYPE III SECRETION SYSTEM 1 REGULATION IN VIBRIO PARAHAEMOLYTICUS
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Vibrio parahaemolyticus is a Gram-negative bacterial pathogen found in contaminated shellfish that causes a self-limiting gastroenteritis. It employs multiple virulence factors in its infection of humans, including two type III secretion systems, which translocate effector proteins into the host cell cytosol. The transcriptional control of type III secretion 1 is through the AraC regulator ExsA, which is functionally homologous to those found in Yersinia spp. and Pseudomonas aeruginosa. Both a distal and proximal promoter were identified that could activate transcription of the exsA gene. In silico analysis and in vitro experiments identified a novel motif within ExsA dependent promoters that is needed to activate transcription of type III secretion system 1 genes vp1687 but not exsD. Using transcriptional fusions, we were able to show that exsA and the genes it regulates are active under conditions known to activate type III secretion. In conclusion, we found that exsA is active during in vitro reporter assays, and ExsA dependent promoters are differentially regulated in secreting conditions.