Integrated morpho-physiological and biochemical description of the mechanisms leading stress responses in cyanobacteria (Arthrospira platensis) upon exposure to Erythromycin.

Erythromycin (ERY) is a widely used antibiotic belonging to the macrolide family and frequently detected in aquatic ecosystems. Despite its prevalence, the toxicological effects of ERY on primary producers, particularly prokaryotic cyanobacteria, remain poorly understood. This study employs a physio-biochemical approach to investigate the impact of ERY exposure on the growth, photosynthesis, oxidative stress, and antioxidant responses of Arthrospira platensis. The results highlight that ERY exposure inhibits the growth of spirulina (A. platensis), resulting in a significant reduction in biomass and pigments. The accumulation of HO, coupled with lipid peroxidation (MDA), indicates oxidative stress in the A. platensis culture due to ERY exposure. The exposure to different doses of ERY over five days leads to marked alterations in the activities of key antioxidant enzymes, including ascorbate peroxidase (APX) and catalase (CAT), as well as detoxifying enzymes like glutathione S-transferase (GST) and peroxidase (POD). Molecular docking studies further substantiate these findings by illustrating the binding affinity of ERY to these enzymes, providing insight into the potential mechanisms underlying the observed enzymatic responses. Furthermore, our results unveil alterations in the energy reserve contents of A. platensis following ERY exposure. Specifically, carbohydrate accumulation show a significant decrease, while protein and lipid levels increase. These changes in bio-component levels reflect the adaptive adjustments made by A. platensis in response to ERY-induced stress. The finding of this study offers a beneficial understanding for a comprehensive evaluation of the toxicity hazards posed by ERY to A. platensis.