Analysis of A Plasmid from Lactobacillus acidophilus and the Construction of Shuttle Vectors

To analyze the endogenous plasmid pDX of Lactobacillus acidophilus, and construct the Escherichia coli-Lactobacillus acidophilus shuttle vector based on the plasmid. In this study, the endogenous plasmid pDX was isolated from Lactobacillus acidophilus XW118, its sequence determination and functional analysis were performed, and then the promotor of plasmid pDX was used to construct a vector that could shuttle between Escherichia coli and lactic acid bacteria. The activity of the endogenous plasmid replicon of L. acidophilus in E. coli and the host range, transformation efficiency and passage stability of the shuttle vector in lactic acid bacteria were studied. The results showed that the size of Lactobacillus acidophilus plasmid pDX was 2062 bp, the GC content was 38.2%, and the plasmid contained four open reading frames (ORFs), which was presumed to be a rolling loop replication plasmid. The copy number of plasmid pDX in L. acidophilus was 31.05. In this study, an E. coli-lactic acid bacteria shuttle vector based on the replicon and promoter of plasmid pDX was constructed. The transformation efficiency of the vector was 0.24×102 to 2.75×103 CFU/μg (plasmid weight), and the plasmid loss rate was 25.45% to 48.36%. In this study, a vector capable of shuttling between E. coli and lactic acid bacteria was constructed, and the promoter of the endogenous plasmid of lactic acid bacteria with activity in E. coli was obtained, which provided a new operational approach for genetic engineering of lactic acid bacteria and metabolic engineering of E. coli.