Sulphur is an essential component of all living cells. The importance of sulphur is well-represented by the sulfhydryl (thiol) functional group, lying at the center of many chemical reactions in biology. Thiol-based reactions have diverse biological functions: thiols in thioredoxins provide reductive power for the synthesis of biological molecules; thiols in coenzyme A facilitate the oxidation of pyruvate and fatty acids to generate energy for living cells; and thiols in glutathione and mycothiol are involved in detoxifying hazardous molecules, as well as maintaining the redox balance of living cells. Additionally, sulphur-containing molecules function as messengers in intracellular and intra-species communation. Sulphur is also a constituent of many other biomolecules like cysteine, methionine, biotin, lipoic acid, molybdopterin, thionucleosides in tRNAs, and thiamine.

Sulphur metabolic pathways of pathogenic bacteria, such as mycobacteria, hold importance both for its biological implications as well as discovering drug targets against enzymes in these pathways. Several enzymes in the sulphur metabolic pathways are essential for mycobacterial survival. The endeavour to map the sulphur metabolic pathways has been greatly facilitated by the emerging information drawn from mycobacterial genome sequencing. Sulphur metabolism plays a role in the pathogenesis of the human pathogen, Mycobacterium tuberculosis, contributing to intracellular survival and virulence. The other mycobacterial species include: Mycobacterium leprae which causes leprosy in humans, Mycobacterium bovis which causes tuberculosis in cattle, Mycobacterium avium which causes disease in immune-compromised individuals, M. bovis Bacille Calmette-Guérin (BCG) which is an attenuated strain of M. bovis used as a vaccine strain and Mycobacterium smegmatis which is a saprophytic non-pathogenic species used extensively as a laboratory model for mycobacterial research.

One-third of the world's population is infected with latent tuberculosis, indicating that the human immune system is capable of controlling the M. tuberculosis infection but not always able to eradicate the bacterium. It has been suggested that sulphur metabolism may have a the role in the prevention of eradication of M. tuberculosis by the human immune system.

from Chapter 7 "Sulphur Metabolism in Mycobacteria" (Ryan H. Senaratne and Kathleen Y. Dunphy) in Mycobacterium: Genomics and Molecular Biology

Further reading: Mycobacterium: Genomics and Molecular Biology

Labels: mycobacteria, mycobacterium, sulphur, tuberculosis