SUMMARY: Two closely related species of mycobacteria, and , were grown under conditions of iron-deficiency (0·02–0·05 μg Fe ml) and iron-sufficiency (2–4 μg Fe ml) in a simple glycerol/asparagine medium. The strain of used was a nonmycobactin producer whereas synthesized between 6–8% of its cell biomass as the lipid-soluble siderophore when grown under iron-limitation. The role of mycobactin for iron-acquisition was examined using both pure and mixed cultures, with cell viability determined following growth at various iron concentrations. , the mycobactin producer, outgrew when iron was readily available. When grown under conditions where iron was limiting, showed a decline in viable cell number compared with its competitor, highlighting its increased requirement for the metal. Some recovery was observed following mycobactin biosynthesis, this being greatly enhanced by the addition of an iron supplement to the growing cells.

Mycobactin biosynthesis allowed to rapidly acquire any additional iron presented to the bacteria when growing under iron-limitation. However, did not synthesize the lipid-soluble siderophore with its iron-requirement satisfied by production of extracellular exochelin.


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