FIG. 3.

Biofilm formation. (A) Eight-hour biofilms produced in DMEM on polystyrene surfaces. (B) Biofilm formation quantified at 8, 24, and 48 h by crystal violet staining and elution. Biofilms were quantified as the OD₅₇₀ of eluted crystal violet, plotted on a logarithmic scale. Strains tested were E. coli K-12 TOP-10 containing pBJ1, the hra1 clone (gray bars), pBJ2, pBJ1 with the surface-exposed region deleted (dotted bars), or pBR322 vector (unshaded bars) as well as wild-type EAEC strain 042 (hatched bars). (C) Surface biofilms formed at the air-water interface in DMEM. Test strains were EAEC strain 042, E. coli K-12 TOP-10 (pBJ1), E. coli K-12 TOP-10 (pBJ1), and negative control E. coli K-12 TOP-10 carrying the pBR322 vector. Values for pBJ2 and pBR322 in TOP-10 were not significantly different from each other (P > 0.05). pBJ1 in TOP-10 produced a significantly greater biofilm than pBJ2 and pBR322 in TOP-10 at 8, 24, and 48 h (P < 0.05). Values obtained for 042 were significantly greater than those for pBJ1 in TOP-10, as well as pBR322 in TOP-10, at all time points (P < 0.05).