【摘要】 在添加乳链菌肽、乳糖及溴甲酚紫的M1 7选择培养基上 ,从 1 97个新鲜牛奶样品中筛选到 3株乳链菌肽抗性菌株 ,PCR扩增证实它们都含有乳链菌肽抗性基因。菌种生理生化特性鉴定及特异性 1 6SrDNAPCR扩增产物的序列测定结果表明这 3株菌都属于乳酸乳球菌乳酸亚种。质粒转化实验发现乳酸乳球菌乳酸亚种TS 1 640中的乳链菌肽抗性基因位于一个约47kb的大质粒pTS50上。BamHI、EcoRI、HindⅢ、NcoI、PstⅠ酶切分析和Southern杂交 ,进一步将乳链菌肽抗性基因定位于pTS50的一个约 1 9kbEcoRI酶切片段中更多还原

【Abstract】 Three nisin\|resistant Lactococcus lactis strains were screened from 197 samples of fresh milk on a selective medium (M17) supplemented with nisin, lactose and bromocresol purple, and were confirmed to have the nisin resistance determinant ( nsr ) by PCR amplification.Physiological and biochemical tests as well as Lactococcus lactis specific 16S rDNA sequence analysis revealed that the three strains all belong to Lactococcus lactis subsp. lactis. A large plasmid, pTS50, was identified in L.lactis subsp. lactis TS1640 which encodes resistance to nisin following electroporation of the total plasmids DNA into L.lactis MG1363.The molecular weight of plasmid pTS50 was estima~ted to be 47kb by restriction analysis of Bam HI, Eco RI, Hin dⅢ, Nco I, Pst I and nsr was localized on a 1.9kb Eco RI fragment by Southern hybridization.更多还原