Study on Antibacterial Activity of Amomum tsao-ko Extracts against Bacillus subtilis and Listeria monocytogenes and Preliminary Investigation of Its Antibacterial Mchanism

The main objective of this study was to preliminarily investigate the antibacterial activity and mechanism of action of Amomum tsao-ko (A. tsaoko) extracts against Bacillus subtilis and Listeria monocytogenes. The results showed that the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of A. tsaoko extracts against B. subtilis and L. monocytogenes were 1.25 mg/mL. Bacterial growth curves revealed that the A.tsaoko extracts had an obvious antibacterial activity against Bacillus subtilis and L. monocytogenes. Furthermore, the mechanism of action of A. tsaoko was evaluated by analyzing its effects on the integrity of cell membrane and cell morphology. The leakage of alkaline phosphatase (AKP) confirmed that the A. tsaoko extracts caused serious damage to the wall structure of B. subtilis and L. monocytogenes. Results of scanning electron microscopy (SEM) manifested that the destructive effect of A. tsaoko extracts on cell morphology and cell integrity of bacterial cells. The results implied that A. tsaoko extracts showed relatively good antibacterial effect on B. subtilis and L. monocytog.