FIG. 3.

Soil populations of P. fluorescens strains Pf0-2 (wild type) and Pf0-5a (adnA mutant) at different depths 1.5 cm from the point of inoculation: 0 to 6.5 cm (A), 6.5 to 13 cm (B), 13 to 15.5 cm (C), 15.5 to 18 cm (D), 18 to 21.5 cm (E), and 21.5 to 25 cm (F). On day 0, strains were mixed and inoculated to 7.84 total log CFU/g of soil. At different times, 0.5- to 1.8-g samples were taken and strains were enumerated by plating serial 10-fold dilutions on Mac agar plates containing rifampin alone or rifampin and kanamycin. Means were determined from four replicates. Significant differences were determined by ANOVA. ∗, ∗∗, statistically significant differences between soil populations of the two strains at P ≤ 0.1 and 0.05, respectively; +, no Pf0-5a detected. Results are representative of two experiments.