Rfal

The gene Rfal codes for the enzyme Waal ligase. In the majority of E.coli, Waal ligase joins the O-antigen to the membrane-bound lipid core molecule. Since the K-12 strain has an insertion mutation in the gene coding for O-antigen, Waal ligase is free to join colanic acid to the lipid core.

The tethering of colanic acid to the cell will faciliate the encapsulation of individual cells confering enhanced acid resistance.