Characterization of Hemolytic Aeromonas sp. MH-8 Responding to the Exposure of Green Tea Catechin, EGCG

The aim of this study was to characterize the hemolytic Aeromonas sp. MH-8 exposed to green tea catechin, epigallocatechin gallate (EGCG). Initially, the hemolytic Aeromonas sp. MH-8 was enriched and isolated from stale fish. Bactericidal effects of MH-8 exposed to EGCG ranging from 1 mg/mL to 4 mg/mL were monitored, and complete bactericidal effects were achieved within 3 h at 3 mg/mL and higher concentrations. SDS-PAGE with silver staining revealed that the amount of lipopolysaccharides increased or decreased in the strain MH-8 treated to different concentrations and exposing periods of EGCG in exponentially growing cultures. The stress shock proteins (70-kDa DnaK and 60-kDa GroEL), which might contribute to enhancing the cellular resistance to the cytotoxic effect of EGCG, were induced at different concentrations of EGCG exposed to cell culture of MH-8. Scanning electron microscopic analysis demonstrated the presence of irregular rod shapes with umbilicated surfaces for cells treated with EGCG. 2-DE of soluble protein fractions from MH-8 cultures showed 18 protein spots changed by EGCG exposure. These proteins involved in chaperons (e.g., DnaK, GroEL and trigger factor), enterotoxins (e.g., aerolysin and phospholipase C precursor), LPS synthesis (e.g., LPS biosynthesis protein and outer membrane protein A precursor), and various biosynthesis and energy metabolism were identified by peptide mass fingerprinting using MALDI-TOF. In consequence, EGCG was found to have substantial antibacterial effects against food-poisoning causing bacterium, hemolytic Aeromonas sp. MH-8. Also the results provide clues for understanding the mechanism of EGCG-induced stress and cytotoxicity on Aeromonas sp. MH-8.