Abstract
The complete nucleotide sequence of cryptic plasmid pLF1 isolated from Lactobacillus plantarum ATCC 14917 has been determined. Sequence analysis revealed 16 ORFs encoding polypeptides larger than 50 amino acids. Based on sequence similarity, three predicated products have been identified in pLF1: orf-66 codes for a cold-shock protein; orf-195 corresponds to a putative integrase/recombinase that shows similarities to integrase/recombinase from plasmids of other Lactobacillus; IS element, ISLp1. No function could be assigned to the other putative ORFs found. As determined by Southern hybridization with pLF1 and ISLp1-radioactively l led probes, some Lactobacillus species show restriction fragment length polymorphism(RFLP). According to the result of hybridization of lysate of Lb. plantarum ATCC 14917 with pLF1-radioactively l led probe, plasmid pLF1 could use a θ-mode of replication.The Emr gene from pE194 was ligated into pBluescriptSK to construct replication origin(RO)-screening vector, pBluSKEⅡ. This plasmid contains pBluescriptSK-derived multiple cloning site, Em-resistance trait, and the lacZ’ gene, which enable direct screening for recombinants in E. coli. Once the recombinant contains a RO from plasmids of Lactobacillus, Emr trait is used as a selection marker as it is transformed into Lactobacillus. In this work, the RO of plasmid pLF1 has not been characterized.