Fig. 2. Expression of VcAer2 in E. coli and its effect on E. coli chemotaxis.

A. Full-length VcAer2 and VcAer2 [165–678] expression in E. coli BT3388 after induction with 50 µM IPTG. Full-length VcAer2 is stably expressed in E. coli, although VcAer2 [165–678] (ΔPAS1) has a higher steady-state level (see Fig. S2A).

B. E. coli BT3388 and E. coli RP437 expressing full-length VcAer2 or VcAer2 [165–678] in tryptone soft agar with 0 or 200 µM IPTG. BT3388 lacks the five native chemoreceptors of E. coli, whereas RP437 is a WT E. coli chemotaxis strain. Plates were incubated at 30 °C for 9 h. VcAer2 does not induce chemotaxis ring formation in E. coli BT3388, but disrupts chemotaxis ring formation by WT E. coli chemoreceptors (the outer Tsr serine ring and the inner Tar aspartate ring). Adding 25 µg ml⁻¹ ALA to the plates (to assist heme incorporation in VcAer2) made no difference to the appearance of the colonies compared to colonies in plates without ALA (not shown).