Fig 7.

Hcp2 is required for the survival of P. syringae pv. tomato DC3000 in a coculture with E. coli, whereas Hcp1 is not required. P. syringae pv. tomato strains were added as droplets on top of an E. coli cell layer in the following order: 1, DC3000 parent strain; 2, Δhcp1 mutant; 3, Δhcp2 mutant; 4, Δhcp1 Δhcp2 double mutant; 5, Δhcp1 + hcp1 complemented mutant; 6, Δhcp2 + hcp2 complemented mutant; 7, Δhcp1 Δhcp2 + hcp1 complemented double mutant; 8, Δhcp1 Δhcp2 + hcp2 complemented double mutant; 9, control (KB only). The bacteria were cocultured on KB agar plates at 25°C for 48 h before photographs were taken, and samples were subsequently prepared for the determination of viable counts. (A) In daylight, the inhibition of E. coli BL21 growth by P. syringae can be detected as a thinner cell layer zone (VIS). Under UV light, P. syringae cells are fluorescent whereas E. coli cells are not. (B) For CFU detection, cocultures were suspended in liquid medium and replated. E. coli colonies were counted after 20 h of incubation at 37°C, and P. syringae colonies were counted after 3 days of incubation at 25°C with rifampin. The results shown are averages of samples from two separate cocultures, and error bars indicate SDs. wt, wild type.