Legionella pneumophila JK-3에 대한 녹차 카테킨 Epigallocatechin Gallate (EGCG)의 항세균 및 프로테옴 효과

Abstract

The objective of this study was to examine the antibacterial and proteomic effects of Legionella pneumophila exposed to a large green tea component, EGCG (epigallocatechin gallate). Initially, the isolate was identified and assigned to Legionella pneumonia JK-3 using the 16S rRNA sequencing. Phylogenetic tree of JK-3 was plotted on 16S rRNA sequencing comparison. EGCG showed a dose-dependent antibacterial effect on L. pneumophila JK-3, while JK-3 treated using 2,000 ug/mL EGCG completely inhibited growth within 3 h of incubation. SEM analysis demonstrated the presence of perforations and irregular rod forms with wrinkled surfaces in cells treated with sublethal concentrations of EGCG. SDSPAGE stained with silver revealed that the amount of lipopolysaccharide in JK-3 increased or decreased according to the concentrations and exposure times of EGCG. Both stress shock proteins (SSPs) (70-kDa DnaK and 60-kDa GroEL) increased in different concentrations of EGCG, whereas the SSPs increased during the early stage as EGCG exposure time of elapsed then gradually decreased. To identify proteins induced by EGCG exposure, 2-DE was applied to soluble protein fractions of JK-3 cultures. Notably, 19 protein spots were either increased or decreased after treatment with EGCG. Using MALDI-TOF mass spectrometry, twelve up-regulated proteins were identified as chaperones, cell envelope proteins, and cell lysis protein. Similarly, seven down-regulated proteins including proteins involved in some energy metabolism and DNA/RNA metabolism were identified. In conclusion, this study provides important clues in understanding of the cytotoxicity mechanisms that affect the antibacterial effect of EGCG exposure, and suggests its use as a phytochemical antibacterial.