Changes in the physiology and gene expression of Microcystis aeruginosa under EGCG stress

• Published in: Chemosphere (Oxford) Vol. 117; pp. 164 - 169
• Main Authors: Lu, Yaping, Wang, Jin, Yu, Yang, Shi, Limei, Kong, Fanxiang
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.12.2014; Elsevier
• Subjects: Action of physical and chemical agents on bacteria; Anti-Bacterial Agents - pharmacology; Bacteriology; Biological and medical sciences; Catechin - analogs & derivatives; Catechin - pharmacology; Damage; Degradation; EGCG; Elevated; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Bacterial - drug effects; Genes; Inhibitory mechanism; Microbiology; Microcystis; Microcystis - cytology; Microcystis - drug effects; Microcystis - growth & development; Microcystis - physiology; Microcystis aeruginosa; Microcystisaeruginosa; Oxidative Stress - drug effects; Photosynthesis; Photosynthesis - drug effects; Reactive Oxygen Species - metabolism; Real-time PCR; Real-Time Polymerase Chain Reaction; Stresses; Tea polyphenol; Microcystisaeruginosa; Inhibitory mechanism; Real-time PCR; EGCG; Tea polyphenol; Phenolic acid; Growth; Toxicity; Epimer; Flavonoid; Medicinal plant; Surface structure; Polyphenol; Dicotyledones; Angiospermae; Cyanobacteria; Bacteria; Mechanism of action; Quantitative real-time PCR; Catechin; Microcystis aeruginosa; Natural compound; Gene expression; Metabolism; Gallic acid derivatives; Gene amplification; Camellia sinensis; Transmission electron microscopy; Morphology; Plant origin; Phenols; Spermatophyta; Antibacterial agent; Molecular biology; Photosynthesis; Theaceae
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.06.040

•EGCG (Epigallocatechin-3-gallate) had a strong inhibitory effect on M. aeruginosa.•EGCG disrupted the cell wall, cell membrane and thylakoid of M. aeruginosa.•EGCG reduced the efficiency of photosynthesis and electron transfer rate.•The expression of some key proteins was influenced by EGCG.•EGCG elevated the level of ROS in M. aeruginosa. EGCG (Epigallocatechin-3-gallate) has an allelopathic inhibitory effect on Microcystis aeruginosa. Cellular structure, physiological and biochemical reactions and gene expression were examined to explore the mechanism of inhibition. As was shown in electron microscopy, the structure of the cell wall, cell membrane and thylakoid was disrupted by EGCG. EGCG also reduced the efficiency of photosynthesis and the electron transfer rate in M. aeruginosa cells, as was determined with a flow cytometer. Quantitative real-time PCR analysis demonstrated that gene expression of the core proteins of the photosynthesis centers PSI and PSII and ATP synthase were reduced, while the expression of the phycobilisome degradation protein A gene (nbl A) was elevated. The expression of the universal stress protein gene increased, which would enhance the adaptive capacity of Microcystis cells to polyphenols and oxidative stress. Furthermore, EGCG elevated the level of reactive oxygen species (ROS) in M. aeruginosa cells, and thus caused oxidative cellular damage. When treated with EGCG at low concentrations (10 and 40mgL−1), the cells were able to activate defense systems to degrade the excess ROS. But at a concentration of 70mgL−1, oxidative stress exceeded tolerance limits, and the cells were severely damaged. We concluded that damage to photosynthesis and oxidative stress were the primary mechanisms for the allelopathic effect of EGCG on M. aeruginosa.