Effect of epigallocatechin gallate on gene expression of Staphylococcus 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.

Mechanism for the antibacterial action of epigallocatechin gallate (EGCg) on Bacillus subtilis.

Catechins are a class of polyphenols and have high anti-bacterial activity against various microorganisms. Here, we report the mechanism for antibacterial activity of epigallocatechin gallate (EGCg) against Gram-positive bacteria Bacillus subtilis, which is highly sensitive to EGCg. Transmission electron microscope analysis revealed that deposits containing EGCg were found throughout the cell envelope from the outermost surface to the outer surface of cytoplasmic membrane. Aggregating forms of proteins and EGCg were identified as spots that disappeared or showed markedly decreased intensity after the treatment with EGCg compared to the control by two-dimensional electrophoresis. Among the identified proteins included 4 cell surface proteins, such as oligopeptide ABC transporter binding lipoprotein, glucose phosphotransferase system transporter protein, phosphate ABC transporter substrate-binding protein, and penicillin-binding protein 5. Observations of glucose uptake of cells and cell shape B. subtilis after the treatment with EGCg suggested that EGCg inhibits the major functions of these proteins, leading to growth inhibition of B. subtilis.