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Published on: August 31, 2015
Mycothiol-dependent mycobacterial response to oxidative stress
Korine S E Ung1, Yossef Av-Gay
1Division of Infectious Diseases, Department of Medicine, The University of British Columbia, D-452 Heather Pavilion East, 2733 Heather Street, Vancouver, BC, Canada V5Z 3J5.
FEBS Letters
|April 29, 2006
Summary
Mycobacterium bovis BCG significantly depletes mycothiol (MSH) under oxidative stress, unlike the tolerant Mycobacterium smegmatis. This study reveals differential MSH responses to oxidants in distinct mycobacteria species.
Area of Science:
- Microbiology
- Biochemistry
- Oxidative Stress Research
Background:
- Mycobacteria possess unique thiol-based redox systems for managing oxidative stress.
- Mycothiol (MSH) is a crucial thiol antioxidant in mycobacteria, maintaining cellular redox balance.
- Understanding MSH's role is vital for combating mycobacterial infections and developing targeted therapies.
Purpose of the Study:
- To investigate the impact of exogenous oxidative stress on mycothiol (MSH) levels and redox balance in mycobacteria.
- To compare the responses of pathogenic Mycobacterium bovis BCG and saprophytic Mycobacterium smegmatis to oxidative challenges.
- To elucidate the differential tolerance mechanisms against oxidants in these species.
Main Methods:
- Exposure of Mycobacterium bovis BCG and Mycobacterium smegmatis cultures to thiol-specific oxidants (diamide) and hydrogen peroxide.
- Quantification of mycothiol (MSH) and its disulfide form, mycothione (MSSM), using biochemical assays.
- Analysis of redox ratios (MSH/MSSM) to assess the cellular redox state under stress conditions.
Main Results:
- Diamide and hydrogen peroxide induced significant depletion (up to 75%) of MSH in Mycobacterium bovis BCG, forming mycothione (MSSM).
- Mycobacterium smegmatis exhibited remarkable tolerance, showing minimal changes in MSH levels and redox ratios upon exposure to the same oxidants.
- Basal MSH/MSSM ratios were established: 50:1 in M. bovis BCG and 200:1 in M. smegmatis, indicating higher basal redox potential in M. smegmatis.
Conclusions:
- Mycobacterium bovis BCG is highly susceptible to exogenous oxidative stress, leading to substantial MSH depletion.
- Mycobacterium smegmatis possesses robust mechanisms to maintain redox homeostasis under oxidative stress.
- Differential regulation of the mycothiol system contributes to varying oxidant tolerance between pathogenic and saprophytic mycobacteria.
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