Impact of melatonin on the hydrogen peroxide treatment efficacy in Microcystis aeruginosa: Cell growth, oxidative stress response, and gene transcription

A study was conducted to determine how melatonin (MLT), a growth regulator, affects Microcystis aeruginosa cell behaviour and how MLT exposed cells respond to hydrogen peroxide (H2O2) treatment. MLT promotes the growth, chl-a content, Fv/Fm values, and microcystins (MCs) production of M. aeruginosa at low concentrations of 1-2.5 mu mol/L but suppresses the growth at high concentrations (5-10 mu mol/L). The cellular and genetic responses of MLT pre-treated cells to H2O2 treatment were examined further. Further research found that the cells pre-treated with MLT were susceptible to a range of growth-promoting, inhibiting and lethal effects when exposed to higher levels of H2O2. A dose-dependent pattern was observed under conditions of 0.05-0.2 mmol/L H2O2 with 0.5-2.5 mu mol/L MLT concentrations to different degrees. High doses of H2O2 (0.2 and 0.3 mmol/L) typically lead to cell lysis and release of MCs in 5.0 and 10 mu mol/L MLT pre-treated cells. A decrease in SOD/CAT activities and an increase in MDA levels validated the growth reduction. Furthermore, higher cell lysis and release of intracellular MCs were observed when H2O2 was increased for 5-10 mu mol/L MLT pre-treated cells. This led to a higher accumulation of extracellular MCs. The results provide insight into how MLT influences H2O2 damage and assist in identifying situations where H2O2 treatment of cyanobacterial blooms is most appropriate.

Automated summary

The study showed that MLT has dual effects on the growth and response of Microcystis aeruginosa, with both promoting and inhibiting effects observed. Cells pre-treated with MLT were more susceptible to the effects of higher H2O2 concentrations, leading to cell lysis and release of MCs. This research provides insights into how MLT influences H2O2 damage and the potential for H2O2 treatment in cyanobacterial blooms.