New insight into the residual inactivation of Microcystis aeruginosa by dielectric barrier discharge.

Lamei Li,Qing Huang,Hong Zhang

doi:10.1038/srep13683

Abstract

We report the new insight into the dielectric barrier discharge (DBD) induced inactivation of Microcystis aeruginosa, the dominant algae which caused harmful cyanobacterial blooms in many developing countries. In contrast with the previous work, we employed flow cytometry to examine the algal cells, so that we could assess the dead and living cells with more accuracy, and distinguish an intermediate state of algal cells which were verified as apoptotic. Our results showed that the numbers of both dead and apoptotic cells increased with DBD treatment delay time, and hydrogen peroxide produced by DBD was the main reason for the time-delayed inactivation effect. However, apart from the influence of hydrogen peroxide, the DBD-induced initial injures on the algal cells during the discharge period also played a considerable role in the inactivation of the DBD treated cells, as indicated by the measurement of intracellular reactive oxygen species (ROS) inside the algal cells. We therefore propose an effective approach to utilization of non-thermal plasma technique that makes good use of the residual inactivation effect to optimize the experimental conditions in terms of discharge time and delay time, so that more efficient treatment of cyanobacterial blooms can be achieved.

Highlights

The energetic particles including negatively charged electrons and positively charged ions, the accompanying intrinsic UV emission and impact waves, chemically active substances such as hydrogen, oxygen, hydrogen peroxide and active radicals such as hydroxyl radical, hydroperoxyl radical, oxygen radical and hydrogen radical are produced during the plasma discharge[2,25,26,27,28]
We initiated this study, in which we employed flow cytometry to evaluate the inactivation efficiency of algal cells treated by DBD, and investigated the mechanism for the inactivation of algal cells by discriminating the dead and apoptotic cells and scrutinizing the residual inactivation effect caused by both hydrogen peroxide and intracellular reactive oxygen species (ROS)
After the DBD treatment, we employed flow cytometry to examine the DBD-treated algal cells, which were labeled with SYBR green I and/or propidium iodide (PI) for discriminating the cells with intact and damaged membrane, respectively

Summary

Introduction

The energetic particles including negatively charged electrons and positively charged ions, the accompanying intrinsic UV emission and impact waves, chemically active substances such as hydrogen, oxygen, hydrogen peroxide and active radicals such as hydroxyl radical, hydroperoxyl radical, oxygen radical and hydrogen radical are produced during the plasma discharge[2,25,26,27,28] These active chemical species can inactivate algal cells as reported by our previous study[2] and other studies[1,12,15]. For these reasons, we initiated this study, in which we employed flow cytometry to evaluate the inactivation efficiency of algal cells treated by DBD, and investigated the mechanism for the inactivation of algal cells by discriminating the dead and apoptotic cells and scrutinizing the residual inactivation effect caused by both hydrogen peroxide and intracellular ROS. Based on the analysis of residual inactivation effect, we attempted to establish a method for providing a useful guide for determination of the optimal experimental conditions regarding discharge and delay times, so that we could achieve the best utilization of the residual inactivation effect and improve the efficiency of plasma technology in bloom control

Methods

Results

Discussion

Conclusion