FIG 8.

Schematic diagram for the functions of OrfA/OrfL and the influences of extracellular matrices. After triggering by a specific external signal, the biosynthesis of albofungin is turned on, wherein the flavin-dependent halogenase OrfA halogenates albofungin, and the MFS efflux pump-like protein OrfL transports the halogenated products outside the cell in a manner similar to the MFS multidrug efflux pumps reported by Pasqua et al. (39). ECM (e.g., lipopolysaccharide [LPS], PIA, and CPS) acting as an antibiotic physical barrier prevents cell wall damage wreaked by albofungins, especially the halogenated products because of high hydrophobicity and less diffusibility (43, 56, 57).