培养时间影响约氏乳杆菌胆汁酸耐受力测定结果的规律及机制

Regularities and Mechanism of The Effects of Incubation Time on The Determination of Bile Acid Tolerance of Lactobacillus Johnsonii

以2株约氏乳杆菌为受试菌株分析了培养时间影响其胆汁酸耐受力测定结果的规律及机制。将菌株接种至含不同类型结合胆汁酸的培养基中,分别培养12 h和18 h,测定活菌数、胆汁酸耐受力、吸光度值、胆汁酸解离率、p H值和细胞膜完整性。结果表明,胆汁酸的抑菌活性与破坏细胞膜完整性有关,培养时间通常会显著影响菌株的胆汁酸耐受力测定结果。培养时间延长后,菌株对二羟基结合胆汁酸的耐受力升高,对三羟基结合胆汁酸的耐受力降低,该现象与培养过程中结合胆汁酸解离及培养基p H值变化有关。培养时间达到12 h后,培养基中的全部结合胆汁酸几乎都被水解为二羟基或三羟基游离胆汁酸,二羟基游离胆汁酸在酸性条件下沉淀析出,因此抑菌能力显著下降。

This study used two strains of Lactobacillus johnsonii as test strains to analyze the regularity and mechanism of the effects of incubation time on the determination of bile acid tolerance of Lactobacillus johnsonii strains.The strains were inoculated in the media with or without different conjugated bile acids for 12 h and 18 h,respectively.Following incubation,viable counts,bile acid tolerance,absorbance values,rates of deconjugation of conjugated bile acids,pH values and membrane integrity were determined.The antibacterial activity of bile acids is related to the disruption of cell membrane integrity.Generally,incubation time has a significant impact on the values of bile acid tolerance of Lactobacillus johnsonii.With the incubation time increasing,the tolerance of strains to conjugated dihydroxy bile acids increased,while the tolerance to conjugated trihydroxy bile acids decreased.These phenomena are related to the deconjugation of conjugated bile acids and the changes in the pH of the media.After 12 h of incubation,almost all the conjugated bile acids in the media were deconjugated into free dihydroxy or trihydroxy bile acids.Free dihydroxy bile acids precipitated under acidic conditions,resulting in a significant decline in antibacterial activity.