microbiology, Vol 142, 2207-2212, Copyright © 1996 by Society for General Microbiology

ARTICLES

The occurrence of carboxymycobactin, the siderophore of pathogenic mycobacteria, as a second extracellular siderophore in Mycobacterium smegmatis

C Ratledge and M Ewing
Department of Applied Biology, University of Hull, UK. c.ratledge@ appbiol.hull.ac.uk

Carboxymycobactin, in which the usual intracellular mycobactin siderophore is modified by possession of a carboxylic acid group, has been isolated as a second extracellular siderophore from culture filtrates of Mycobacterium smegmatis grown under iron-deficient conditions. (The primary siderophore is an exochelin which is a trihydroxamate, pentapeptide derivative). There may be up to 12 similar molecules produced with differing chain lengths that can be recognized by HPLC or HPTLC. The amount of carboxymycobactin is about 20 times higher when cultures are grown with glycerol instead of glucose. Formation is maximal with an initial pH of the medium of about 8.4. The proportion of carboxymycobactin to the total siderophore produced-- mainly exochelins--is maximally 10% (usually 10-25 micrograms ml(-1)). Formation of both extracellular siderophores (exochelin and carboxymycobactin) and of the intracellular mycobactin is maximal at the same initial concentration of iron added to the medium, 0.05-0.1 micrograms Fe ml(-1), though exochelin is synthesized 24 h in advance of both carboxymycobactin and mycobactin.

This article has been cited by other articles:

				J. Bacon, L. G. Dover, K. A. Hatch, Y. Zhang, J. M. Gomes, S. Kendall, L. Wernisch, N. G. Stoker, P. D. Butcher, G. S. Besra, et al. Lipid composition and transcriptional response of Mycobacterium tuberculosis grown under iron-limitation in continuous culture: identification of a novel wax ester Microbiology, May 1, 2007; 153(5): 1435 - 1444. [Abstract] [Full Text] [PDF]

				B. B. D. LaMarca, W. Zhu, J. E. L. Arceneaux, B. R. Byers, and M. D. Lundrigan Participation of fad and mbt Genes in Synthesis of Mycobactin in Mycobacterium smegmatis J. Bacteriol., January 15, 2004; 186(2): 374 - 382. [Abstract] [Full Text] [PDF]

				I. Smith Mycobacterium tuberculosis Pathogenesis and Molecular Determinants of Virulence Clin. Microbiol. Rev., July 1, 2003; 16(3): 463 - 496. [Abstract] [Full Text] [PDF]

				G. M. Rodriguez, M. I. Voskuil, B. Gold, G. K. Schoolnik, and I. Smith ideR, an Essential Gene in Mycobacterium tuberculosis: Role of IdeR in Iron-Dependent Gene Expression, Iron Metabolism, and Oxidative Stress Response Infect. Immun., July 1, 2002; 70(7): 3371 - 3381. [Abstract] [Full Text] [PDF]

				J. J. De Voss, K. Rutter, B. G. Schroeder, H. Su, Y. Zhu, and C. E. Barry III The salicylate-derived mycobactin siderophores of Mycobacterium tuberculosis are essential for growth in macrophages PNAS, February 1, 2000; 97(3): 1252 - 1257. [Abstract] [Full Text] [PDF]

				T. Adilakshmi, P. D. Ayling, and C. Ratledge Mutational Analysis of a Role for Salicylic Acid in Iron Metabolism of Mycobacterium smegmatis J. Bacteriol., January 15, 2000; 182(2): 264 - 271. [Abstract] [Full Text]

				S. Yu, E. Fiss, and W. R. Jacobs Jr. Analysis of the Exochelin Locus in Mycobacterium smegmatis: Biosynthesis Genes Have Homology with Genes of the Peptide Synthetase Family J. Bacteriol., September 1, 1998; 180(17): 4676 - 4685. [Abstract] [Full Text]