Mitochondrial dysfunction redirects proton transport and energy homeostasis in Saccharomyces cerevisiae under...

Mitochondrial function is crucial for the regulation of energy metabolism, proton homeostasis, and stress adaptation in Saccharomyces cerevisiae. This study demonstrates the role of mitochondria in modulating cellular responses to varying extracellular pH (3.0, 5.0, 6.5) and glucose availability (0.5%, 2%). Results indicate that mitochondrial deficiencies in Δhap4 and ρ⁰ mutants selectively impair growth under acidic pH and 0.5% glucose conditions, whereas wild-type cells maintain pH-independent growth. Mitochondrial impairment redistributes intracellular H⁺ homeostasis regulation to plasma membrane and cytosolic H⁺-ATPases in a glucose- and pH-dependent manner, with ρ⁰ cells exhibiting maximal reliance on non-mitochondrial ATPases. The N, N'- dicyclohexylcarbodiimide (DCCD)-sensitive J_H⁺ scales inversely with glucose availability, reflecting energy demand under nutrient limitation and acid stress. ρ⁰ cells exhibit the highest alcohol dehydrogenase activity to regulate the redox balance in response to non-functional mitochondria. The highest total H⁺-ATPase activity measured in ρ⁰ cells at pH 6.5 and 0.5% glucose conditions, combined with proton flux data, indicates the upregulation of plasma membrane and cytosolic ATPases activity for maintaining proton motive force and intracellular pH due to a complete loss of F_oF₁-ATPase contribution. These results pave the way for the construction of robust S. cerevisiae yeast strains to varying glucose and extracellular pH conditions.