Influence of inhibitors of lipid biosynthesis on the production of avermectins in Streptomyces avermitilis

Streptomyces avermitilis was grown in the presence of four inhibitors of fatty acid biosynthesis (p- chlorophenoxyacetic, DL -2-(p- chlorophenoxy)- propionic , 2-( p-chlorophenoxy)-2-methyl-propionic and p-fluotophenoxyacetic acids). The production of total lipids was inhibited and the cellular content of individual types of fatty acids was altered by these compounds. The anteiso-acid content decreased by up to one-half, whereas the content of iso-odd acids increased 10-fold in the presence of inhibitors. The decrease in anteiso-acids was accompanied by increased production of avermectins having a s-butyl group in the side chain (type ‘a’ avermectins). It was concluded that the common precursor, 2-methylbutyryl-CoA, was diverted from the biosynthetic pathway of fatty acids to that of avermectins.