Figure. Box plot chart showing effects of ciliates on the transfer frequency of plasmid-mediated quinolone-resistance genes between Escherichia coli strain J53 and qnrB-positive Klebsiella oxytoca strain (white boxes) or qnrA-positive E. coli strain (black boxes). Box plots are divided by medians (black or white bars) into upper quartile and lower quartile ranges. Error bars indicate minimum and maximum values. Asterisks indicate a statistically significant difference (p<0.05) between treated and untreated cultures.