Abstract：Lactobacillus paracasei MA3, harboring two natural plasmids, was isolated from fresh milk using selective medium SL. In order to obtain the complete sequence, the unknown small plasmid pMA3 was digested with ScaI and ligated with vector pBK-CMV. The complete sequence of pMA3 revealed to be 5809bp in length with GC content of 39.54%. The computer analysis revealed that pMA3 harbored four ORFs, one of them designated Rep3, which is replication initiation protein. Sequence analysis results determined the highly homologous similarity of Rep protein and the tandem direct repeats, which demonstrated that pMA3 belongs to the pUCL-287 subfamily of theta-type replicons. This plasmid has been deposited in GenBank under Accession No.EU255257.This research has made a basis for developing the food-grade expressing vector with independent intellectual property rights.
