FIG. 3.

T4P-mediated twitching assay for migration up a gradient of PE and oleic acid. A PE (A, B, and C) or oleic acid (D) gradient was first established to the right of the round/oval ring marking where the P. aeruginosa strains were placed on the top of the agar 24 h after the placement of the lipid (see Materials and Methods). The PAO1 wild-type strain (A) and PAO1 strains (ΔaceA [B and D] and ΔaceA att::aceA⁺ [C]) are depicted. The arrows in panel B point to the transitional region between the area where there is a complete inhibition of twitching motility (toward the PE gradient) and the area where general twitching is occurring in the absence of PE. Note that the area of complete inhibition of twitching motility is not seen when the chemoattractant is an LCFA (i.e., oleic acid) as shown in panel D. The bar in panel A represents 2 mm and provides a gauge of distance between the phospholipid shown to the right and the bacteria on the left.