培养条件对保加利亚乳杆菌中胞外肽酶PrtB基因表达的影响

Effect of Culture Conditions on Expression of the Extracellular Peptidase Gene PrtB from Lactobacillus bulgarian

目的:选择实验室保藏的保加利亚乳杆菌,探究不同的培养条件对其关键酶PrtB基因表达的影响。方法:利用实时荧光定量PCR测定生长时期、氮源、初始pH值(5.6,5.9,6.2和6.5)和培养温度(30,37,42℃和45℃)对PrtB基因表达的影响。试验结果表明,保加利亚乳杆菌LB08012、LB08014和LB08016从对数初期到稳定期,PrtB基因的表达量显著下调(P<0.05);N缺乏条件与正常MRS培养条件相比,PrtB的表达量呈现明显增加的趋势(P<0.05),而添加酪蛋白胨与正常MRS培养条件相比,PrtB的表达量显著下调(P<0.05);在初始培养pH值为5.9,6.2和6.5中的表达量与对照组(pH5.6)相比,LB08006、LB08007、LB08012和LB08016菌株的PrtB的表达量为增加(P<0.05),而LB08014、LB08015和LB08017菌株为降低(P<0.05);在37,42℃和45℃时,LB08007、LB08012、LB08014和LB08015菌株的PrtB的表达量为先上升后下降,而LB08006、LB08016和LB08017为先上升后下降的趋势,45℃时PrtB的表达量最低,趋于0,较对照组(30℃)下降10.7倍。

Objective:The effects of different culture conditions on expression of key extracellular gene PrtB of the protein hydrolysis system of Lactobacillus bulgarian was evaluated in the present experiment.Methods:Real-time PCR technology was used to determine target gene expression among different strains under different growth periods and different nitrogen sources,initial pH(5.6,5.9,6.2,6.5)and temperature(30,37,42,45℃).The experimental results showed that the expression levels of PrtB were significantly reduced in three strains of Lactobacillus bulgaricus LB08012,LB08014 and LB08016 from the early logarithm phase to the stable phase(P<0.05).Under the condition of N lack of culture,the expression of PrtB was significantly higher(P<0.05)than that of normal state culture.In addition,the expression of PrtB was significantly decreased(P<0.05)under the cultivation condition of adding the casein.The expression quantities of PrtB in the medium of pH5.9,6.2 and 6.5 were significantly increased(P<0.05)in strains LB08006,LB08007,LB08012 and strain LB08016,however,the expression quantities of PrtB in strain LB08014,LB08015 and strain LB08017 was significantly decreased(P<0.05)compared to the control group(pH 5.6).In liquid MRS medium at different temperatures,the expression of prtb of strains LB 08007,LB 08012,LB 08014 and LB 08015 increased first and then decreased at 37℃,42℃a nd 45℃,while the prtb expression of strains LB 08006,LB 08016 and LB 08017 increased first.After the reduction.At a temperature of 45℃,the expression level of PrtB tended to be 0,which was 10.7 times lower than that of the control group(30℃).