FIG 1.

DHMA is a chemoattractant for EHEC 86-24. The chemotaxis response of EHEC was investigated using the plug-in-pond assay. EHEC cells expressing GFP were suspended in CB and incubated with an agarose plug containing either CB alone (control) or CB plus a signal molecule. The accumulation of cells at the plug edge was observed after 30 min with an inverted fluorescence microscope. The increase in the intensity of fluorescence at the plug boundary serves as a qualitative measure of the attractant response to the chemical in the plug. (A) Plug with CB plus 500 μM DHMA; (B) plug with CB only (negative control); (C) plug with CB plus 100 μM l-serine (positive control). The images shown are from one representative experiment of three independent experiments.