Figure 2

Chemotaxis of E. coli is inhibited by the expression of Ppr or Pph. (A) The chemotactic wild type strain E. coli MM500 was transformed with the plasmids pBAD-Ppr (lanes 1 and 2), pBAD-Pph (lanes 3 and 4) and pBAD-Pph H670A (lanes 5 and 6). Cells were grown in TB medium to an OD₆₀₀ = 0.5, 0.2% fructose (lanes 1, 3 and 5) or 0.2% arabinose (lanes 2, 4 and 6) was added, and growth was continued for 3 hours. Protein expression was analyzed by SDS-PAGE and Coomassie blue staining. The positions of molecular weight markers are indicated. (B) TB swarm agar plates containing either 0.2% arabinose or 0.2% fructose as indicated were inoculated with the following cells. Upper panels: E. coli MM500 transformed with plasmids pBAD-Ppr, pBAD-Pph or pBAD-PphH670A, respectively. Lower panels: Untransformed MM500 cells, MM500 transformed with plasmids pBAD or pBAD-KdpE, respectively. To develop chemotactic rings the plates were incubated for 6 hours at 37°C.