(A) Comparison of avermectin production in various S. avermitilis strains grown in FM-I medium for 10 days. WT, wild-type strain ATCC31267; WT/pKC1139, ATCC31267 carrying control plasmid pKC1139; D576, SAV576 deletion mutant; D576/pSET152-576, complementation strain of D576; WT/pKC1139-576, SAV576 overexpression strain. (B) Western blotting analysis of SAV576 and AveR protein in cells grown in FM-I for 6 days. Approximately 100 µg total protein of each sample was subjected to Western blot and Coomassie Blue staining for the loading control. AveR-D19, aveR mutant. (C and D) Effect of SAV576 deletion on avermectin production (C) and growth (D) of S. avermitilis grown in FM-II. Solid squares, ATCC31267; Solid circles, D576; Solid triangles, complementation strain of D576.