大蒜有机硫化物对解淀粉芽孢杆菌的抑菌作用及机理

Antibacterial activity and mechanism of garlic organic sulfide against Bacillus amyloliquefaciens

【目的】明确大蒜有机硫化物(GOS)对豆制品优势腐败解淀粉芽孢杆菌Bacillus amyloliquefaciens的抑菌活性及作用机理。【方法】通过抑菌圈法和二倍稀释法测定GOS对菌株的抑菌活性、最低抑菌浓度(MIC)和最低杀菌浓度(MBC),并分析其对细菌生长曲线及胞外蛋白酶活性的影响;分析GOS处理后解淀粉芽孢杆菌代谢活性、碱性磷酸酶活性、β–半乳糖苷酶活性及胞外溶液电导率的变化,并结合扫描电镜观察菌体形态变化,探讨GOS对解淀粉芽孢杆菌的抑菌机理。【结果】3 g/mL的GOS对解淀粉芽孢杆菌DY1a和DY1b的抑菌圈直径分别为31.7和25.7 mm,MIC均为30 mg/mL,MBC分别为240和480 mg/mL。30 mg/mL GOS对菌株DY1a和DY1b胞外蛋白酶活性的抑制率分别为47.3%和15.6%,使细菌细胞代谢活性(D490 nm)分别下降了2.771和4.091,胞外碱性磷酸酶活性分别提高了0.029和0.036 U/mL,胞外β-半乳糖苷酶活性(D420 nm)分别提高了0.047与0.016,胞外溶液电导率分别提高了0.060和0.031 mS/cm。扫描电镜结果显示,GOS处理后的菌株细胞表面出现皱缩、孔洞式塌陷和破裂。【结论】大蒜有机硫化物对解淀粉芽孢杆菌抑制作用明显,其抑菌机理与影响细菌细胞壁、细胞膜的通透性和完整性,干扰细菌生理代谢活动有关。

【Objective】To explore antibacterial activity and mechanism of garlic organic sulfide(GOS)against Bacillus amyloliquefaciens.【Method】The antimicrobial activity,minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of GOS against B.amyloliquefaciens strain were determined using the inhibition zone method and the double dilution method,and its inhibitory effects on bacterial growth curve and extracellular protease activity were evaluated.Metabolic activity,alkaline phosphatase activity,β-galactosidase activity,extracellular conductivity and thallus morphological changes observed through scanning electron microscope of B.amyloliquefaciens treated with GOS were investigated for elucidating antibacterial mechanism of GOS against B.amyloliquefaciens.【Result】Diameter of inhibitory zone of GOS against B.amyloliquefaciens DY1a and DY1b were 31.7 and 25.7 mm respectively,MIC of both strains were 30 mg/mL,MBC were 240 and 480 mg/mL,respectively.The inhibition rate of 30 mg/mL GOS on DY1a and DY1b extracellular protease activity were 47.3%and 15.6%respectively.After treatment with 30 mg/mL GOS,metabolic activity(D490 nm)decreased by 2.771 and 4.091 respectively,extracellular alkaline phosphatase activity increased by 0.029 and 0.036 U/mL,extracellularβ-galactosidase activity(D420 nm)increased by 0.047 and 0.016 respectively and the extracellular electrical conductivity increased by 0.060 and 0.031 mS/cm respectively.The results of SEM showed that the surface of bacteria cells treated with GOS had shrinkage,cavity collapse and rupture.【Conclusion】The excellent antibacterial effect of GOS against B.amyloliquefaciens may be attributed to irreversible damage to cell wall and cell membrane and alterations of cell physiological metabolism.