REGULATION OF XENOBIOTIC EFFLUX SYSTEMS IN ESCHERICHIA COLI IN RESPONSE TO ENVIRONMENTAL CHANGES
4 , 2016-03-24 , 法政大学大学院理工学・工学研究科
The RND-type efflux system of bacteria plays a major role in multidrug resistance. However, it has been unclear how an RND-ternary complex is assembled and the expression of genes encoding its components is regulated under physiological conditions. In this study, I asked how newly synthesized transporter molecules assemble into a ternary complex and how indole acts as a signaling molecule for the expression of the inducible transporter gene acrD. I demonstrated that the expression of new transporter molecules can destabilize preexisting RND-type efflux complexes to facilitate transporter exchange. This exchange is suppressed by substrates of the transporter that is already in the complex. Moreover, I found that the expression of acrD is induced by the intracellular ccumulation of indole via the two-component regulatory system BaeSR. These mechanisms may enable the bacterium to rapidly acquire the resistance to a newly encountered toxic compound. Next I examined the cellular protein imaging using labeling methods other than fluorescent proteins. I demonstrated that FlAsH a fluorescently labeled ligand (Ser-FAM) for the amino acid chemoreceptor are useful for imaging signaling components in Vibrio cholerae.