Short Duration Exposure of Vibrio Cholerae to Small Intestine Conditions and the Effect on Cholera Toxin and Stringent Response Gene Expression

Context: Vibrio cholerae is the causative agent of cholera, the epidemic diarrheal disease. The colonization and subsequent diarrheal symptoms are produced due to toxin coregulated pilus (TCP) and cholerae toxin (CT) respectively. Regulation of their expression involves a complex regulon, toxR, which is composed of toxT, a transcription factor that directly initiates transcription of the ct and tcp genes; and its upstream regulators tcpP and toxT, which require transcription factors tcpH and toxS. Objective: Most research in V. cholerae to date has shown expression of these virulence factors after a long exposure to small intestine conditions. The goal of this work was to determine changes that happen immediately after V. cholerae is exposed to conditions found in the small intestine. Design: Experimental Setting: MUCOM biologic research lab Methods: Deletions were made in regulon genes toxR, tcpPH, and toxT, as well as the stringent response regulators relA, spoT and relV. Expression of CT and TCP were quantified via the expression of the first gene in the ctx and tcp operons using real time PCR. Results: In tcpPH knock outs, there was still expression of TCP, similar to that of wild type. Moreover, with the loss of toxT, tcpPH, toxR, or a combination of toxR/toxT, toxR/tcpPH expression levels of CT were either absent or very minimal. Conclusions: These results show differences from those in which these strains are present in small intestine conditions for longer periods of time, particularly for the stringent response null strains. This may indicate that initial adjustment to the small intestine is affected by stringent response activity, but longer term expression of virulence factors do not require stringent response but only the toxR regulon. Further investigation will be required for understanding how V. cholerae use environmental signals to regulate virulence gene expression