Effects of H2O2 on growth, metabolic activity and membrane integrity in three strains of Microcystis aeruginosa

Abstract

The application of hydrogen peroxide (H 2 O 2 ) as a management tool to control Microcystis blooms has become increasingly popular due to its short lifetime and targeted action. H 2 O 2 increases intracellular reactive oxygen species resulting in oxidative stress and subsequently cell death. H 2 O 2 is naturally produced in freshwater bodies as a result of photocatalytic reactions between dissolved organic carbon and sunlight. Previously, some studies have suggested that this environmental source of H 2 O 2 selectively targets for toxigenic cyanobacteria strains in the genus Microcystis. Also, past studies only focused on the morphological and biochemical changes of H 2 O 2 -induced cell death in Microcystis with little information available on the effects of different H 2 O 2 concentrations on growth, esterase activity and membrane integrity. Therefore, this study investigated the effects of non-lethal (40-4000 nM) concentrations on percentage cell death; with a focus on sub-lethal (50 μM) and lethal (275 μM; 500 μM) doses of H 2 O 2 on growth, cells showing esterase activity and membrane integrity. The non-lethal dose experiment was part of a preliminary study. Results showed a general effect of dose and time dependent relationship in all three Microcystis strains post H 2 O 2 treatment. H 2 O 2 resulted in a significant increase in intracellular reactive oxygen species, decreased chlorophyll a content, decreased growth rate and esterase activity. Interestingly, at sub-lethal (50 µM H 2 O 2 treatment), percentage of dead cells in microcystin-producing strains were significantly higher (p<0.05) from non-microcystin producing strains at 72h. These findings further cement our understanding of the influence of H 2 O 2 on different strains of Microcystis and its impact on membrane integrity and metabolic physiology; important to future toxic bloom control programmes.

Hydrogen peroxide can be a plausible biomarker in cyanobacterial bloom treatment

“…7 ). It was nearly same as the lethal level of the previous studies 35 , 39 . A higher protein level was not observed with higher H 2 O 2 concentration levels in the present study.…”

“…Previous researchers obtained the lethal H 2 O 2 dosage for cyanobacteria by laboratory incubations under different H 2 O 2 concentrations; cyanobacterial chlorophyll declined to nearly half after an 18 h incubation with approximately 30 µmol L −1 of H 2 O 2 1 , 40 or after a 4 h incubation with 100 µmol L −1 of H 2 O 2 2 H 2 O 2 delayed fluorescence decay with 0.1 µmol of H 2 O 2 L −1 7 . At the same time, the Fv/Fm value substantially declined with 100 µmol of H 2 O 2 L −1 41 , and dead cells increased with 275 µmol of H 2 O 2 L −1 39 . Cyanobacteria were in a lethal condition 1 , 2 and sub-lethal at concentrations exceeding 50 µmol of H 2 O 2 L −1 39 .…”

“…At the same time, the Fv/Fm value substantially declined with 100 µmol of H 2 O 2 L −1 41 , and dead cells increased with 275 µmol of H 2 O 2 L −1 39 . Cyanobacteria were in a lethal condition 1 , 2 and sub-lethal at concentrations exceeding 50 µmol of H 2 O 2 L −1 39 . All previous experimental results reveal that cyanobacterial biomass is degraded with higher H 2 O 2 concentrations; however, the H 2 O 2 concentration threshold varies widely from 1 to 1000 µmol L −1 .…”

“…The artificial endorsement of H 2 O 2 has a high potential to suppress cyanobacterial blooms with less effect on other organisms compared to other controlling methods 35 – 39 . Previous researchers obtained the lethal H 2 O 2 dosage for cyanobacteria by laboratory incubations under different H 2 O 2 concentrations; cyanobacterial chlorophyll declined to nearly half after an 18 h incubation with approximately 30 µmol L −1 of H 2 O 2 1 , 40 or after a 4 h incubation with 100 µmol L −1 of H 2 O 2 2 H 2 O 2 delayed fluorescence decay with 0.1 µmol of H 2 O 2 L −1 7 .…”

Hydrogen Peroxide Can Be a Plausible Biomarker in Cyanobacterial Bloom Treatment

“…The arti cial endorsement of H 2 O 2 has a high potential to suppress cyanobacterial blooms with less effects on other organisms compared to other controlling methods [35][36][37][38][39] Natural H 2 O 2 formation has been identi ed in aquatic ecosystems as a photolysis of dissolved organic carbon (DOC) exposed to UV 3,[42][43][44] reported that the H 2 O 2 production varies with the nutrient content of the water body. However, the H 2 O 2 concentration of these waters was in the magnitude of mmol L - 1 4,26,45 .…”