Fig. 3.

FNR-regulated biofilm formation in ETEC. (A) A picture of spontaneously occurring biofilm production when H10407 is grown anaerobically at 37 °C with shaking. Image is representative of more than 10 independent replicates. An fnr mutant produces more biofilm than wild type and this phenotype can be complemented by expressing the fnr gene from the pBad18 plasmid in the fnr:kan mutant background. All depicted growth included 0.2% arabinose for consistency with the induced complemented strain. (B) Quantification of ETEC biofilm formation exemplified in Fig. 5A using optical density readings of crystal violet-stained biofilms as described in Materials and Methods. All growth represents three independent biological replicates grown with 0.2% arabinose for consistency with the induced complementation strain. The relative amounts of biofilm produced by various ETEC H10407 strains in the indicated conditions are shown compared with wild-type ETEC H10407 biofilm production, which is set as 1 as a reference. Statistical significance was determined by one-way ANOVA with a Tukey multiple comparison test (P values <0.05 were considered significant) and error bars represent the SEM.