Figure 1. Construction and growth curve of rex-deletion mutant.

(A) Method (schematic) used for rex deletion. Long arrows: genes and their directions. Short black arrows: positions of primers used for cloning of exchange regions and confirmation of gene deletion (see M&M). Rectangles: exchange regions used for rex deletion. (B,C) Growth (B) and avermectin production (C) of rex-related mutant strains in liquid fermentation medium II. Values shown are mean ± SD from three replicate flasks.