Inactivation ofompXCauses Increased Interactions of Type 1 FimbriatedEscherichia coliwith Abiotic Surfaces

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Abstract
During the initial steps of biofilm formation, bacteria have to adapt to a major change in their environment. The adhesion-induced phenotypic changes in a type 1 fimbriatedEscherichia colistrain included reductions in the levels of several outer membrane proteins, one of which was identified as OmpX. Here, the phenotypes of mutant strains that differ at theompXlocus were studied with regard to adhesion, cell surface properties, and resistance to stress and antimicrobial compounds. The kinetics of adhesion were measured online by an extended quartz crystal microbalance technique for wild-type and mutant strains with a fimbriated or nonfimbriated background. Deletion ofompXled to significantly increased cell-surface contact in fimbriated strains but to decreased cell-surface contact in a nonfimbriated strain. Phenotypic characterization of theompXmutant demonstrated thatompXinterferes with proper regulation of cell surface structures that play a key role in mediating firm contact of the cell with a surface (i.e., type 1 fimbriae, flagellae, and exopolysaccharides). These phenotypic changes were accompanied by increased tolerance to several antibiotic compounds and sodium dodecyl sulfate. Based on these results, we propose that changes in the composition of outer membrane proteins during fimbria-mediated adhesion may be part of a coordinated adaptive response to the attached mode of growth.