Early steps in the biosynthesis of mycobactins P and S.

1. Lysine is readily incorporated into mycobactins P and S. Incorporation is into the hydroxamic acid moieties only and is equal in the mycobactic acid and cobactin portions of the molecule. 2. 2-Amino-6-hydroxyaminohexanoic acid is not taken up by cells of Mycobacterium phlei and is not detectable in extracts of cells actively synthesizing mycobactin. 3. The most abundant material derived from lysine that can be detected in such cell extracts is an N(6)-acyl-lysine. Cells grown in the presence of iron contain markedly less of this material than do those grown under conditions of iron deficiency. 4. When added to growing cultures of M. phlei the N(6)-acyl-lysine is readily incorporated into mycobactin. 5. The hydroxy acid of cobactin P is derivable from propionate.