Investigation of mycobactin production and biosynthetic pathway. (A) TLC of mycobactins extracted from various mycobacterial cultures labeled with 7-14C salicylic acid. The bracketed region includes labeled species present in M. smegmatis, M. tuberculosis, and M. avium species but not M. avium subsp. paratuberculosis. S, secreted (medium); C, cell associated; MAA, M. avium subsp. avium; MI, M. intracellulare; MAH, M. avium subsp. hominissuis. (B) TLC of mycobactins extracted from M. intracellulare, MAP-cattle K10, and MAP-sheep S6756 and P465. The bracketed region includes labeled species present in M. intracellulare species but not M. avium subsp. paratuberculosis. S, secreted (medium); C, cell associated. (C) Organization of the mbt clusters in M. avium subsp. hominissuis, MAP-cattle (MAPc), and MAP-sheep (MAPs). Striped arrows represent protein products with less than 80% amino acid similarity.