FIGURE 1.

Transfer frequencies (TFs) obtained from conjugation experiments in LB media using aquatic donor communities from urban and agricultural areas of the La Paz River basin and E. coli CV601 (recipient). Bars represent mean values obtained from three independent conjugation experiments. Error bars represent the standard deviation of the mean from the two mating replicates included in each independent experiment. A higher number of transfer events per recipient was obtained using bacterial donors from the urban site (Mann-Whitney U Test, p = 0.02). For both sampling sites, TFs varied significantly between independent experiments. Asterisks (**) show the significantly between difference from the first independent experiment (1st exp) by Brown-Forsythe ANOVA p = 0.03, post hoc Tukey test. There was no significant difference in TF between the second and third independent experiments.