Comparing the Effects and Mechanisms of Action of Permanganate, Chlorine, and Hydrogen Peroxide on the Membrane Integrity of Pseudanabaena sp. Cells

Preoxidation is usually used to remove cyanobacteria in drinking waterworks. However, the effects and mechanisms of action of oxidants on the membrane integrity of cyanobacterial cells are scarcely known, which may lead to cell damage and facile release of plenty of harmful metabolites. This study investigated the kinetics of Pseudanabaena cell lysis under separate exposure to potassium permanganate (KMnO4), sodium hypochlorite (NaClO), and hydro-gen peroxide (H2O2). Mechanisms of interaction between them and the Pseudanabaena cell surface at the cellular and molecular levels were then defined. Results showed that cell lysis matched a two-stage kinetic model under KMnO4 or H2O2 exposure, and cells remained intact below a certain exposure threshold; in comparison, the log value of cell concentration decreased linearly with NaClO exposure. Pseudanabaena cell damage rates followed the order NaClO > KMnO4 > H2O2. Permanganate ions primarily reacted with cell-bound organic matter and then oxidized cell membrane, whereas neutral HClO produced by NaClO can permeate the membrane of algal cells and damage cell membrane quickly. As for H2O2, although H2O2 can gradually permeate the algal cell membrane, the reactivity between H2O2 and cell membranes was low. The algal cell membrane remained intact in the initial stage and then was damaged when H2O2 accumulation reached a certain level.