FIG 1.

Biofilm formation protects E. coli against C. elegans predation. Approximately 25 L1- to L2-stage C. elegans worms were moved to the center of an agar plate on which four UTI89 strains had grown for 2 days under biofilm-inducing conditions. At 3-day intervals, plates to which C. elegans had been added and C. elegans-free control plates were harvested for CFU counts, and the percentage of survival was calculated (A). Each data point is an average of biological triplicates, and error bars represent standard deviations. A Student's t test was employed to determine significant differences between strains at day 15, and asterisks represent a P value of <0.05. An image was taken of each strain at each time point from a representative C. elegans-positive plate that was harvested at day 15 (B).