| Abstrakt: |
Aims: To characterize the 21‐kDa iron‐regulated cell wall protein in Mycobacterium smegmatis co‐expressed with the siderophores mycobactin, exochelin and carboxymycobactin upon iron limitation. Methods and Results: Mycobacterium smegmatis, grown in the presence of 0·02 μg Fe ml−1 (low iron) produced high levels of all the three siderophores, which were repressed in bacteria supplemented with 8 μg Fe ml−1 (high iron). Exochelin, the major extracellular siderophore was the first to rise and was expressed at high levels during log phase of growth. Carboxymycobactin, a minor component in log phase iron‐starved M. smegmatis continued to rise when cultured for longer periods, reaching levels greater than exochelin. Iron‐starved bacteria expressed a 21‐kDa iron‐regulated protein (IrpA) that was identified as Clp protease subunit (MSMEG_3671) and characterized as a receptor for ferri‐exochelin. Conclusions: Ferri‐exochelin is the preferred siderophore in M. smegmatis and this ferri‐exochelin: IrpA machinery is absent in Mycobacterium tuberculosis. Significance and Impact of the Study: Exochelin machinery is functional in M. smegmatis and the carboxymycobactin–mycobactin machinery is the sole iron uptake system in M. tuberculosis. The absence of the ferri‐exochelin: IrpA system in the pathogen signifies the importance of the carboxymycobactin–mycobactin system machinery in M. tuberculosis. [ABSTRACT FROM AUTHOR] |
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