Exopolysaccharide production is required for development of Escherichia coli K-12 biofilm architecture

Although exopolysaccharides (EPSs) are a large component of bacterial biofi lms, their contribution to biofilm structure and function has been examined for only a few organisms. In each of these cases EPS has been shown to be required for cellular attachment to abiotic surfaces. Here, we undertook a genetic approach to examine the potential role of colanic acid, an EPS of E scherichia coli K-12, in biofilm formation. Strains either proficient or de ficient in colanic acid production were groan and allowed to adhere to abio tic surfaces and were then examined both macroscopically and microscopicall y. Surprisingly, we found that colanic acid production is not required for surface attachment. Rather, colanic acid is critical for the formation of t he complex three-dimensional structure and depth of E. coli biofilms.