Alexander Mircea Petrescu

• TolC is a component of the protein complex that forms the main bacterial efflux system involved in expelling out of the cell numerous harmful antibacterial chemicals such as antibiotics and detergents. TolC is the outer membrane component of the system and it connects with an inner membrane energy-demanding pump, which can be either an ABC transporter or a proton antiporter. A periplasmic membrane fusion protein seals the connection of the two. TolC is able to bind a multitude of such transporters which have very different substrate specificities thus TolC part-taking in the efflux of dozens of substrates. This makes TolC be a main participant in the phenomenon of multidrug efflux and a better understanding of its behavior in vivo is thus required. In the present study, the spatial localization and time-resolved dynamics of TolC production in live cells is described. This is achieved by labeling the TolC protein genomically with an oxidation-resistant variant of GFP, superfolder GFP. The labelled protein is fully functional and shows a growth medium-dependent expression. Furthermore, certain antibiotics increase its production in a concentration-dependent manner. This is the first time such a behavior was shown and opens new ways for further research.