Isolation and characterization of carboxymycobactins as the second extracellular siderophores in Mycobacterium smegmatis

The structure of a chloroform-extractable siderophore from the supernatant of a nonpathogenic mycobacteria, Mycobacterium smegmatis, has been determined and it closely resembles the structure of mycobactin, the intracellular siderophore found in all mycobacteria. The difference in structures is that the extracellular siderophore has a family of short carboxylic chains attached to the mycobactin nucleus instead of a long alkyl chain and hence the name `carboxymycobactin' is proposed to distinguish it from mycobactin itself as well as from the major siderophore that is produced - exochelin MS.