Abstract: Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were isolated from commercial yogurts using selective media, and physiological and biochemical tests, sugar fermentation experiments and 16S rDNA homology analysis were used to identify the isolated strains. Genotyping of the strains was performed by pulsed field gel electrophoresis (PFGE). It was found that both Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus were detected in all yogurt samples. Streptococcus thermophilus had the same genotyping only in two yogurts, while other Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were different in different yoghurts. The results showed that PFGE was an effective method for genotyping of different strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus.

Key words: yogurt; Lactobacillus bulgaricus; Streptococcus thermophilus; genotyping by PFGE

摘要： 采用选择性培养基分离酸乳中的保加利亚乳杆菌和嗜热链球菌，并利用生理生化和糖发酵实验结合16S rDNA同源性分析对分离所得菌株进行鉴定，获得保加利亚乳杆菌和嗜热链球菌分离菌株。利用脉冲场凝胶电泳（pulsed field gel electrophoresis，PFGE）分别对保加利亚乳杆菌和嗜热链球菌分离株进行基因分型。结果表明：所检测的酸乳样品中均含有保加利亚乳杆菌和嗜热链球菌；仅有2 种酸乳的嗜热链球菌为同一菌株，其余酸乳中的保加利亚乳杆菌及嗜热链球菌均为不同菌株。PFGE可以对保加利亚乳杆菌和嗜热

关键词: 酸乳；保加利亚乳杆菌；嗜热链球菌；PFGE基因分型