Effect of hydrogen peroxide on Microcystic aeruginosa: Role of cytochromes P450.

Cyanobacterial bloom has been rising as a worldwide issue owing to its adverse effects to water quality and ecological health. To solve this problem, hydrogen peroxide (H2 O2 ) has been considered as a potential algaecide because no by-products are generated after treatment and because it kills cyanobacteria selectively. In addition, cytochromes P450 (CYPs) was reported to be related with H2 O2 , but the roles of CYPs in the regulation of H2 O2 in cyanobacteria have yet to be investigated. In this study, the CYPs suicide inhibitor 1-aminobenzotriazole (ABT) was added to the representative cyanobacteria Microcystis aeruginosa (M. aeruginosa) exposed to H2 O2 . The results showed that CYPs mediates the effects of H2 O2 on M. aeruginosa. To be exact, the addition of ABT induced greater inhibitory effects on the growth and higher reactive oxygen species levels in M. aeruginosa comparing to those treated with H2 O2 alone. At the same time, photosynthetic parameters significantly decreased, and the content of extracellular microcystins (MCs) increased but the total MCs decreased due to the combined effect of H2 O2 and ABT. ABT also intensified the aggregation of Fe, which might explain the effects on photosynthesis and synthesis of MCs. Furthermore, the transcriptional levels of MCs-synthesis genes (mcyA and mcyD) decreased but MCs-release gene (mcyH) increased, and photosynthetic genes (psaB, psbD1 and rbcL) decreased, which confirmed the effects on the MC production/release and electron transport of photosynthesis, respectively. In summary, this study illuminated the mediation role of CYPs in the adverse effects on M. aeruginosa induced by H2 O2 , thus providing new theoretical basis for the explanation of H2 O2 as potential algaecide.