Fig 3.

Effect of manure containing sulfadiazine (SDZ) on frequencies of sulfonamide resistance transfer from bulk soil (BS) and rhizosphere (RH) bacteria to E. coli K-12 CV601gfp. Transfer frequencies per recipient cell were determined by filter matings on days 48 and 132 for field plots sown with grass and maize. Differing letters indicate significant differences of means in pairwise comparisons (Tukey test; P < 0.05) for each day. Treatments of soil with control manure and manure containing SDZ are indicated by light and dark gray, respectively. Error bars indicate standard deviations of results for 4 replicates (except maize rhizosphere treatment without SDZ, day 48, where n = 3).