title: Construction and characterization of shuttle plasmids for lactic acid bacteria and Escherichia coli.
abstract: The chimeric plasmid pBN183 was first constructed in Escherichia coli by ligating the BamHI-digested E. coli plasmid pBR322 and a Bg/II-linearized streptococcal plasmid, pNZ18. The pBN183 transformed E. coli to ApR at a frequency of (8.2 +/- 1.2) x 10(5) colony forming units (CFU)/microgram DNA. Electrotransformation of Streptococcus thermophilus with pBN183 yielded CmR, ApS clones at a frequency of (2.6 +/- 0.3) x 10(1) CFU/microgram DNA. Plasmid screening with pBN183-transformed S. thermophilus clones revealed that ca. 70% of these transformants contained deleted plasmids. Plasmid pBN183A, a pBN183 deletion mutant lacking one copy of a tandemly arranged, highly homologous DNA sequence, was isolated for further study. It transformed E. coli to ApR and S. thermophilus to CmR with frequencies of (4.8 +/- 0.1) x 10(5) and (8.1 +/- 0.2) x 10(2) CFU/microgram DNA, respectively. Screening of S. thermophilus transformants did not show the presence of deleted plasmids. Based on the structure of pBN183A, a new shuttle plasmid, pDBN183, was constructed from pBN183 by removal of the small (1.2 kb) Sa/I fragment. Transformation frequencies of pDBN183 were (5.0 +/- 1.3) x 10(5) and (4.6 +/- 0.2) x 10(2) CFU/microgram DNA with E. coli and S. thermophilus, respectively. In contrast to the parent pBN183, only 17% of the pDBN183-transformed S. thermophilus contained deleted plasmids. Plasmid copy numbers of the three vectors in E. coli were estimated at 17-18 per chromosome. The three plasmids conferred ApR and CmR to E. coli, but only CmR to S. thermophilus. The insertion of a Streptomyces cholesterol oxidase gene (choA) into pDBN183 did not affect the plasmid's stability in Lactobacillus casei, but resulted in deletion of the recombinant DNA in S. thermophilus.
authors.affiliation: U.S. Department of Agriculture, ARS, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118.
authors.forename: D K
authors.initials: DK
authors.lastname: Solaiman
authors.forename: G A
authors.initials: GA
authors.lastname: Somkuti
authors.forename: D H
authors.initials: DH
authors.lastname: Steinberg
mesh_terms: D002789:Cholesterol Oxidase / Q000235:genetics; D003001:Cloning, Molecular / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics*; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D007780:Lacticaseibacillus casei / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D013291:Streptococcus / Q000235:genetics*; D014170:Transformation, Genetic
chemical_list: D007773:Lactates; D019344:Lactic Acid; D002789:Cholesterol Oxidase