SEM micrographs showing the biofilms developed by EACF 205 and EAEC strains. A- Single biofilm formed by traA-positive EAEC strain 340-1. Arrows indicate the putative F pili. Note that pili were not limited to the polar region of the bacteria and, at times, were viewed to intertwine forming thicker structures. B- Enhanced biofilm developed by coculture of EACF 205 and traA-positive EAEC strain 340-1. White arrowhead indicates the incipient formation of curli fibers and arrows indicate the putative F pili. C- Single biofilm developed by traA-negative prototype strain 17-2. D- Single biofilm formed by EAEC 340-1 displaying curli fibers (white arrowheads). Curli fibers were shown to mediate cell-cell adherence and interaction to abiotic surface. Arrow indicates a putative F pilus.