Antioxidant Status of Cyanobacteria Strains During Long-Term Cultivation in Nitrogen-Free Media

This study examines the antioxidant status of four Nostoc and Desmonostoc strains during long-term cultivation in nitrogen-depleted media. Growth rates, retinol and α-tocopherol content, fatty acid composition, and activities of antioxidant enzymes were analysed. The results showed that all tested strains adapted to nitrogen limitation using various cellular mechanisms. Specifically, the strain Nostoc sphaeroides exhibited the highest specific growth rate and elevated glutathione peroxidase activity. The Nostoc commune and Desmonostoc caucasicum strains displayed higher superoxide dismutase activity, suggesting robust antioxidative capabilities. Additionally, Desmonostoc caucasicum exhibited unique adaptive strategies, such as elevated succinate dehydrogenase activity. Generally, fatty acid composition changes showed divergent lipid peroxidation vulnerabilities among the studied strains. Principal component analysis highlighted clear distinctions among the strains in terms of their antioxidant capacities and metabolic adjustments. High retinol content correlated positively with increased catalase activity and fatty acid saturation, whereas α-tocopherol concentration was linked to succinate dehydrogenase activity. The obtained results underscore the robustness of cyanobacterial antioxidant defence systems and highlight their metabolic adaptations under nitrogen deprivation. Understanding these responses offers insight into potential biotechnological applications, such as biofertilizers or therapeutics.