ISOLATION AND CHARACTERIZATION OF A PLASMID FROM LACTOBACILLUS-FERMENTUM CONFERRING ERYTHROMYCIN RESISTANCE

Lactobacillus fermentum is a lactic acid bacterial species commonly fo und in the digestive tracts of pigs and rodents and also present in ma n. We characterized a 5.7-kb plasmid, pLEM3, conferring erythromycin r esistance, which was isolated from a porcine strain of L. fermentum. P lasmid pLEM3 established efficiently in L. fermentum, conferred high-l evel erythromycin resistance (MIC > 1 mg/ml), and was segregationally stable. A deletion derivative of pLEM3, called pLEM5, was constructed and found to be as genetically stable as the parent. A multiple clonin g site was inserted into pLEM5, generating plasmid pLEM7. Nucleotide s equence determination of pLEM5 revealed similarities with known genes. The replicon itself is a member of the pC194 family of rolling circle plasmids. The region responsible for erythromycin resistance was 98.2 % identical to the emr gene of conjugative transposon Tn/545. (C) 1997 Academic Press.