Escherichia coli O8-antigen enhances biofilm formation under agitated conditions.

Bacterial surface components have a major role in the development of biofilms. In the present study, the effect of Escherichia coli O8-antigen on biofilms was investigated using two E. coli K-12 derived strains that differed only in the O8-antigen biosynthesis. In the presence of O8-antigen both bacterial adhesion and biofilm formation slightly decreased under static conditions whereas a substantial increase in adhesion and biofilm formation was observed under agitated conditions. It was noted that, irrespective of the O8-antigen status, the hydrophobic interactions played an important role in bacterial adhesion under both static and agitated conditions. However, under agitated conditions, the extent of bacterial adhesion in the O8-antigen bearing strain was predominantly determined by the electrostatic interactions. Results showed that the presence of O8-antigen decreases the surface hydrophobicity and surface charge. Moreover, O8-antigen facilitates adhesion on hydrophilic and hydrophobic surfaces as revealed through tests with modified substrata. Our results indicate that O8-antigen, which appears dispensable for biofilm formation under static conditions, actually enhances E. coli biofilm formation under agitated conditions.