Fig. 2.

Responses of different E. coli strains to the novel attractants. The fluorescence intensities in region 2 emitted by different strains responding to novel attractants were normalized against the fluorescence intensity of cells responding to blank buffer. The relative intensities in region 2 emitted by RP437 (A) and UU1624 (B) are significantly stronger than the blank buffer, but those emitted by RP2361 (C) are similar to the blank buffer (mean ± SEM; n ≥ 2). As a control, the responses of RP437 and UU1624 to AMA, as well as RP2361 to l-serine (Ser), were also measured. The source concentrations were 1 mM for AMA and Ser; 10 mM for AMPA, GSA, FIA, NMA, and NFA; and 100 mM for IOTA. The compound concentration range for cells in region 1 was 0% to 50% of the source concentration (*Significance at P < 0.05 vs. blank buffer by one-way ANOVA).