A novel vector for lactic acid bacteria that uses a bile salt hydrolase gene as a potential food-grade selection marker.

摘要

A novel vector pM4aB for lactic acid bacteria was developed using a bile salt hydrolase gene from Lactobacillus plantarum as a potential food-grade selection marker. The 3.0-kb pM4aB consisted of the replicon of Lactobacillus plasmid pM4, a multiple cloning site and the bsh gene, which was constructed by elimination of a 5.5-kb non-food-grade DNA fragment from an 8.5-kb intermediate vector pBEmpM4aB. For electroporation into Lactobacillus paracasei X9, a high transformation efficiency of 4.0 +or- 1.0 x 104 CFU/ mug plasmid DNA was yielded with 0.1% (w/v) glycodeoxycholic acid sodium selection. A high segregation stability of the vector was also observed as only 0.1% plasmid was lost after 50 generations of growth without selection pressure. The application potential of pM4aB was further confirmed by expression of a catalase gene from Lactobacillus sakei in L. paracasei. These results revealed that the novel vector pM4aB constructed in this study would be a useful tool for genetic modification of the industrially important LAB.