Laboratory evolution of copper tolerant yeast strains

Area of Science:

• Microbiology
• Biotechnology
• Biochemistry

Background:

• Copper (Cu) tolerance in yeast strains has potential applications in biotechnology, including functional food production.
• Understanding copper metabolism is crucial for studying related human diseases.
• This study investigates the molecular and physiological factors conferring copper tolerance in baker's yeasts.

Purpose of the Study:

• To characterize the effects of copper exposure on natural strains of Candida humilis and Saccharomyces cerevisiae.
• To investigate the molecular and physiological mechanisms of natural and acquired copper tolerance in yeasts.
• To compare the responses of different yeast species to copper stress.

Main Methods:

• Exposure of natural yeast strains (Candida humilis, Saccharomyces cerevisiae) to varying copper sulfate (CuSO4) concentrations.
• Evolution of yeast strains to achieve hyper-resistance to copper.
• Measurement of copper accumulation, antioxidant enzyme activity (superoxide dismutase, catalase), and copper-binding proteome profiling.

Main Results:

• Candida humilis demonstrated natural robustness, tolerating up to 1 g·L-1 CuSO4, accumulating >7 mg Cu/g biomass, and possessing high constitutive antioxidant enzyme levels.
• Saccharomyces cerevisiae growth was inhibited at low copper concentrations, but evolved strains showed increased antioxidative enzymes.
• Evolved hyper-resistant Candida cells exhibited decreased antioxidant activities, and both evolved yeasts tolerated up to 2.5 g·L-1 CuSO4, accumulating significant intracellular copper.

Conclusions:

• Different mechanisms, including control of copper uptake, altered oxidative stress response enzymes, and changes in the copper-binding proteome, contribute to metal tolerance.
• Acquired copper tolerance in yeasts involves distinct physiological and molecular adaptations.
• Yeast background significantly influences the physiological and molecular reactions to copper exposure.