FIG. 4.

Overall avermectin production in wild-type S. avermitilis (A and B), high-producer strain ATCC 31780 (C), and semi-industrial strain L-9 (D) cultured in modified MF medium for 8 days. Symbols: □, no plasmid; ▴, orfX disrupted; •, pPRA4 introduced by electroporation of intact cells; ○, pPRA4 introduced by polyethylene glycol-mediated transformation; ▪, pIJ702 introduced by polyethylene glycol-mediated transformation. Thiostrepton addition had no effect on the growth of the transformants, and each plot represents the mean values of three independent experiments. Bars indicate standard error.