Effect of donor inoculation and subsequent plasmid transfer on the degradation of 2,4-D in the nutrient-amended A- and B-horizon soil. The data points and error bars show the means and standard deviations based on data from duplicate microcosms. ▴, noninoculated soil plus 2,4-D; ⧫, soil plus 2,4-D plus pEMT1::lacZ; ■, soil plus 2,4-D plus pJP4::lacZ.