Role of tol genes in cloacin DF13 susceptibility of Escherichia coli K-12 strains expressing the cloacin DF13-aerobactin receptor IutA.

IutA is the outer membrane protein receptor for ferric aerobactin and the bacteriocin cloacin DF13. Although the same receptor is shared, ferric aerobactin transport across the outer membrane in Escherichia coli is TonB dependent, whereas cloacin DF13 transport is not. We have recently observed that tolQ is required for cloacin DF13 susceptibility (J.A. Thomas and M.A. Valvano, FEMS Microbiol. Lett. 91:107-112, 1992). In this study, we demonstrate that the genes tolQ, tolR, and tolA, but not tolB, tolC, and ompF, are required for the internalization of cloacin DF13 and they are not involved in the transport of ferric aerobactin.