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Characterization of exochelins of the Mycobacterium bovis type strain and BCG substrains
J Gobin1, D K Wong, B W Gibson
1Department of Medicine, School of Medicine, University of California, Los Angeles, California 90095, USA.
Abstract:
Pathogenic mycobacteria must acquire iron in the host in order to multiply and cause disease. To do so, they release abundant quantities of siderophores called exochelins, which have the capacity to scavenge iron from host iron-binding proteins and deliver it to the mycobacteria. In this study, we have characterized the exochelins of Mycobacterium bovis, the causative agent of bovine and occasionally of human tuberculosis, and the highly attenuated descendant of M. bovis, bacillus Calmette-Guérin (BCG), widely used as a vaccine against human tuberculosis. The M. bovis type strain, five substrains of M. bovis BCG (Copenhagen, Glaxo, Japanese, Pasteur, and Tice), and two strains of virulent Mycobacterium tuberculosis all produce the same set of exochelins, although the relative amounts of individual exochelins may differ. Among these mycobacteria, the total amount of exochelins produced is greatest in M. tuberculosis, intermediate in M. bovis, and smallest in M. bovis BCG.
Insights
Pathogenic mycobacteria use exochelins to scavenge iron for growth. Mycobacterium tuberculosis produces the most exochelins, followed by Mycobacterium bovis, and then bacillus Calmette-Guérin (BCG).
Area of Science:
- Microbiology
- Infectious Diseases
- Biochemistry
Background:
- Pathogenic mycobacteria require host iron for multiplication and disease.
- Exochelins are siderophores released by mycobacteria to acquire iron.
- Iron acquisition is crucial for mycobacterial virulence.
Purpose of the Study:
- To characterize the exochelins produced by Mycobacterium bovis and its attenuated descendant, bacillus Calmette-Guérin (BCG).
- To compare exochelins production in M. bovis, BCG substrains, and Mycobacterium tuberculosis.
Main Methods:
- Characterization of exochelins from M. bovis and BCG substrains.
- Comparative analysis of exochelins production levels.
Main Results:
- All tested strains of M. bovis, M. bovis BCG, and M. tuberculosis produce the same set of exochelins.
- Relative amounts of individual exochelins varied among strains.
- Total exochelins production was highest in M. tuberculosis, intermediate in M. bovis, and lowest in M. bovis BCG.
Conclusions:
- Mycobacterium bovis and BCG produce a conserved set of exochelins.
- Differential production of exochelins correlates with the virulence of these mycobacterial species.
- Exochelins are key virulence factors in mycobacterial iron acquisition.