How Type 1 Fimbriae Help E. coli Adhere to Interfaces?

Adhesion of bacteria to interfaces is the initial step in the formation of biofilms, in pathogenic infection, and in the bioremediation of oil spills. Bacteria use a variety of surface appendages to attach to surfaces, and the level of expression of these appendages varies in response to environmental conditions and external stimuli. Type 1 fimbriae, one such appendage, help bacteria attach to cells and to evade antibiotics during initial infection and hence are widely studied as a critical factor in pathogenic virulence. Here, we present a tunable approach to quantify how changes in the expression level of type 1 fimbriae alter the ability of bacteria to adhere to interfaces. A plasmid that enables inducible expression of E. coli MG1655 type 1 fimbriae was transformed into fimbriae-deficient mutant MG1655ΔfimA. The level of fimH gene expression in the engineered strain was tuned by changing the concentration of inducer isopropyl β-D-1- thiogalactopyranoside (IPTG). We find that increasing the degree of fimbriation results in a significant decrease in cell motility, but enhances the ability of bacteria to adhere to solid surfaces and to oil-water interfaces. The tunable extent of fimbriation accessible with these engineered strains may prove useful for physical measurements probing the effects of adhesin expression on biofilm formation over surfaces and on biodegradation of hydrocarbons.