Nitrogen Stress-Induced Modulation of Antimicrobial and Antioxidant Activities in Aphanothece Sp.: Insights from Phytochemical Profiling and Molecular Docking

Abstract

The modulation of nutrient availability represents a critical factor influencing the metabolic pathways and production of bioactive compounds in algae. This study aimed to examine the impact of nitrogen stress on the antimicrobial and antioxidant properties, phytochemical composition, and molecular docking assessments of the cyanobacterium Aphanothece sp. The results demonstrated that Aphanothece sp. when cultivated under conditions of nitrogen deficiency, exhibited markedly elevated antimicrobial and antioxidant activity compared to the control. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of the extracts obtained from algae on E. coli ATCC 25922 were found to be 25 mg mL- 1 when the sample was grown in nitrogen medium and 6.25 mg mL- 1 when grown in a nitrogen-free medium. The IC50 value obtained from DPPH free radical scavenging assay changed from 137.30 f 16.22 mg mL- 1 to 20.07 f 1.55 mg mL- 1 in nitrogen-free medium. According to the results of GC-MS analysis, the major components in the extract obtained from the algae grown in the nitrogen-free environment were 13,16-Octadecadiynoic acid, methyl ester (35.10 %) and Hexadecanoic acid, methyl ester (22.65 %), while the major components in the extract obtained from the algae grown in nitrogen-containing medium were Protopine (65.68 %) and 3,6,9,12,15-Pentaoxabicyclo(15.3.1) henicosa-1(21),17,19-triene-2,16-dione (12.15 %). The findings suggest a range of binding energies and interaction profiles for the compounds in the extracts with their molecular targets, which may have implications for their potential significance in therapeutic applications. The results of this study indicate that nitrogen stress can be employed as a strategic tool to enhance the production of valuable bioactive compounds in Aphanothece sp., thereby underscoring its potential applications in biotechnology and drug development.