Apisada Kitichalermkiat1, Mao Katsuki1, Jun Sato2, Takumi Sonoda2, Yoshimitsu Masuda1, Ken-Ichi Honjoh1, Takahisa Miyamoto3. 1. Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan. 2. Safety Science Research, R&D, Kao Corporation, Akabane 2606, Haga-Gun, Ichikai-Machi, Tochigi, Japan. 3. Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan. Electronic address: tmiyamot@agr.kyushu-u.ac.jp.
Abstract
OBJECTIVES: Staphylococcus aureus is an important nosocomial pathogen that produces various extracellular toxins. Epigallocatechin gallate (EGCg) is a polyphenol that is abundant in green tea. EGCg displays strong antibacterial activity against Gram-positive bacteria. The effect of EGCg on gene expression by S. aureus was investigated to clarify the mechanism underlying its antibacterial action. METHODS: Microarray analysis was performed on S. aureus treated with or without 500mg/L EGCg. Differentially expressed genes were identified and their changes at the transcription level were confirmed using real-time quantitative polymerase chain reaction (qPCR). The membrane potential of cells treated with or without EGCg were observed under fluorescence microscopy. RESULTS: Microarray analysis revealed that EGCg treatment of S. aureus resulted in increased and decreased transcription of 75 and 72 genes, respectively. Increased transcription exceeding 1-log2-fold change of genes related to membrane transport included gntP, gntK, rumA, SAOUHSC_02723, SAOUHSC_01311, and vraS. Decreased transcription was observed in genes involved in toxin production and stress response (hlgA, SAOUHSC_01110, hly, hlgB, efb, and hlgC). All changes in transcription were confirmed using real-time qPCR. The membrane potential of S. aureus treated with 500mg/L EGCg markedly decreased, indicating that EGCg damaged the cell membrane. CONCLUSIONS: S. aureus increases the transcription of genes involved in membrane transport to recover membrane function. EGCg can potentially serve as a natural antibacterial agent to control the growth and toxin production of S. aureus.
OBJECTIVES:Staphylococcus aureus is an important nosocomial pathogen that produces various extracellular toxins. Epigallocatechin gallate (EGCg) is a polyphenol that is abundant in green tea. EGCg displays strong antibacterial activity against Gram-positive bacteria. The effect of EGCg on gene expression by S. aureus was investigated to clarify the mechanism underlying its antibacterial action. METHODS: Microarray analysis was performed on S. aureus treated with or without 500mg/L EGCg. Differentially expressed genes were identified and their changes at the transcription level were confirmed using real-time quantitative polymerase chain reaction (qPCR). The membrane potential of cells treated with or without EGCg were observed under fluorescence microscopy. RESULTS: Microarray analysis revealed that EGCg treatment of S. aureus resulted in increased and decreased transcription of 75 and 72 genes, respectively. Increased transcription exceeding 1-log2-fold change of genes related to membrane transport included gntP, gntK, rumA, SAOUHSC_02723, SAOUHSC_01311, and vraS. Decreased transcription was observed in genes involved in toxin production and stress response (hlgA, SAOUHSC_01110, hly, hlgB, efb, and hlgC). All changes in transcription were confirmed using real-time qPCR. The membrane potential of S. aureus treated with 500mg/L EGCg markedly decreased, indicating that EGCg damaged the cell membrane. CONCLUSIONS:S. aureus increases the transcription of genes involved in membrane transport to recover membrane function. EGCg can potentially serve as a natural antibacterial agent to control the growth and toxin production of S. aureus.