Characterization of stress processes of Phaffia rhodozyma stress-resistant mutant

Area of Science:

• Microbiology
• Biochemistry
• Oxidative Stress Research

Background:

• Phaffia rhodozyma is known for astaxanthin production.
• Oxidative stress impacts microbial growth and survival.
• Carotenoids are often associated with antioxidant properties.

Purpose of the Study:

• To investigate the oxidative stress resistance of a carotenoid-less Phaffia rhodozyma mutant.
• To determine the factors contributing to enhanced stress resistance in the mutant.
• To compare the antioxidant defense mechanisms between the mutant and its parental strain.

Main Methods:

• Comparative analysis of oxidative stress resistance using menadione, H2O2, and K2Cr2O7.
• Quantification of intracellular reactive oxygen species (ROS) and glutathione levels.
• Measurement of catalase specific activity under uninduced and induced conditions.

Main Results:

• The carotenoid-less mutant (MCP 325) demonstrated significantly higher resistance to oxidative stressors compared to the astaxanthin-producing parental strain (MCP 324).
• The mutant exhibited lower superoxide, hydroxyl radical, and glutathione content, but higher peroxide concentration under uninduced conditions.
• Elevated specific catalase activity was observed in the mutant, which was further induced by peroxide treatment, unlike the parental strain.

Conclusions:

• The enhanced oxidative stress resistance in the Phaffia rhodozyma mutant is not solely due to the absence of carotenoids.
• A secondary mutation likely affects the regulation of antioxidant systems, including catalase activity and ROS scavenging.
• Despite metabolic alterations, the mutant maintained growth rates comparable to the parental strain.