Abstract:

In this study, for the first time, we investigated the effect of temperature (15–42 ℃) on the expression of core
genes of the integrative and conjugative element (ICE, ICEVpaChn1) in Vibrio parahaemolyticus CHN25 using real time
polymerase chain reaction (real-time PCR). The results revealed distinct expression patterns of the tested genes. The eex
gene involved in the entry exclusion system was strongly inhibited by more than 10 folds when the bacterium was incubated
at the temperatures below or above 37 ℃. Along with increasing temperature in the range of 15–37 ℃, the expression of
int, traI, rumA, and traG genes was enhanced, and reached the highest level at 37 ℃ as the optimal growth temperature for
V. parahaemolyticus CHN25. In contrast, increasing temperature could significantly repress the expression of the gene
encoding a repressor protein SetR that can stimulate the activators of the int gene (SetC and SetD) and promote the conjugation
and transfer of ICEVpaChn1. In addition, self-transmissible activity of the ICE was likely inhibited when the bacterium was
grown at temperatures lower than 15 ℃ or above 37 ℃. The results of this study will facilitate better understanding of the
molecular mechanism underlying the effects of environment stresses on the conjugative transfer of ICEs.

Key words: Vibrio parahaemolyticus, integrative and conjugative elements, real-time polymerase chain reaction, gene expression