Toxic mechanisms of the antiviral drug arbidol on microalgae in algal bloom water at transcriptomic level

Increasing antivirals in surface water caused by their excessive consumption pose serious threats to aquatic organisms . Our recent research found that the input of antiviral drug arbidol to algal bloom water can induce acute toxicity to the growth and metabolism of Microcystis aeruginosa , resulting in growth inhibition, as well as decrease in chlorophyll and ATP contents. However, the toxic mechanisms involved remained obscure, which were further investigated through transcriptomic analysis in this study. The results indicated that 885–1248 genes in algae were differentially expressed after exposure to 0.01–10.0 mg/L of arbidol, with the majority being down-regulated. Analysis of commonly down-regulated genes found that the cellular response to oxidative stress and damaged DNA bonding were affected, implying that the stress defense system and DNA repair function of algae might be damaged. The down-regulation of genes in porphyrin metabolism, photosynthesis , carbon fixation , glycolysis, tricarboxylic acid cycle , and oxidative phosphorylation might inhibit chlorophyll synthesis, photosynthesis, and ATP supply, thereby hindering the growth and metabolism of algae. Moreover, the down-regulation of genes related to nucleotide metabolism and DNA replication might influence the reproduction of algae. These findings provided effective strategies to elucidate toxic mechanisms of contaminants on algae in algal bloom water.