Recently, Prof. Huang Qing’s group from Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS) proved important role of 1O2 in synergistic antimicrobial mechanism when studying the fungicide mechanism of cold atmospheric plasma (CAP).
The related research results have been published in Science of the Total Environment.
CAP is highly effective in inactivating harmful microorganisms. By producing a variety of reactive oxygen species (ROS), CAP can induce oxidative stress in microorganisms, thus leading to different modes of death. It is important to understand the role of ROS in the killing of harmful microorganisms, which can provide the guidance for high-efficiency microbial killing in the environment.
In recent years, Huang Qing's group have conducted systematic research on the mechanism and application of non-thermal plasma microbial disinfection and sterilization.
In this study, the respective roles of ROS generated by plasma in killing fungi, including hydroxyl radical (·OH), singlet oxygen (1O2), hydrogen peroxide (H2O2) and superoxide anion (O2-), were scrutinized, respectively. Particularly, the synergistic effect of singlet oxygen with other plasma-generated ROS in fungi inactivation was found and explained.
Based on the previous study, they studied the generation of ROS (·OH, 1O2, H2O2, O2-) by CAP carefully, and specifically explored their relationship with various intracellular ROS (·OH, 1O2, H2O2, O2-) over time.
It was found that among the plasma-generated ROS, ·OH mainly causes fungal inactivation by disrupting the wall membrane structure, while 1O2 has a synergistic effect with other ROS in killing fungi. Plasma-generated 1O2 can induce the depolarization of mitochondrial membrane potential (MMP), and the degree of MMP depolarization determines the fate of the fungi.
During short-term of plasma treatment, mild mitochondrial damage leads to the onset of apoptosis. In contrast, during prolonged treatment, plasma-generated ·OH can severely damage cell membranes and elevated level of 1O2 can induce severe depolarization of MMP, which can then lead to an increase in intracellular O2- and Fe2+, resulting in cell necroptosis.
Another finding by the team was that 1O2 could lead to intracellular protein aggregation and the production of necrosome RIP1/RIP3, ultimately leading to necroptosis.
This study improved the understanding of the fungicidal mechanism of CAP and provides theoretical guidance for more applications of plasma technology.
This research work was mainly supported by Anhui Provincial key research and development plans and China Postdoctoral Science Foundation.
Figure 1: Patterns of intracellular ROS (·OH, 1O2, H2O2, O2-) changes in yeast. (Image by XU Hangbo)
Figure 2: Mechanism of CAP-induced apoptosis and necroptosis. (Image by XU Hangbo)