Exochelin-mediated iron acquisition by the leprosy bacillus, Mycobacterium leprae

Exochelins, water-soluble siderophores of mycobacteria, were isolated and partially purified from culture filtrates of iron-deficiently grown cultures of Mycobacterium neoaurum NCTC 10439 and an armadillo-derived Mycobacterium (ADM 8563). Two biologically active fractions mediating iron uptake were isolated from each bacterium which not only were able to transport iron into the producing organism but also into suspensions of Mycobacterium leprae isolated from armadillo liver. The rate of exochelin-mediated iron uptake into M. leprae was about 1.5% of the rate observed into the producing organisms. The process of iron uptake appears to be by facilitated diffusion as it was not inhibited by HgCl2, NaN3, KCN, dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone. Since no uptake of iron occurred into iron-sufficient ADM cells, this may indicate that M. leprae, as recovered from an animal tissue, had been growing iron-deficiently in order for iron uptake to have been demonstrated in vitro.