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KMID : 0545120030130030457
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Journal of Microbiology and Biotechnology
2003 Volume.13 No. 3 p.457 ~ p.462
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Molecular Characterization of Plasmid from Bifidobacterium longum
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Park MS
Moon HW/Ji GE
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Abstract
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The complete nucleotide sequence of a plasmid pMG1 isolated from Bifidobacterium longum MG1 has been determined. This plasmid composed of 3862 base pairs with 65.1% of G+C content harbors two major open reading frames (ORF) encoding putative proteins of 29 kDa (ORF I) and 71 kDa (ORF II). ORF I showed relatively high amino acid sequence homology with replication proteins of other plasmids from Gram-positive and -negative bacteria. Upstream of ORF I four sets of tandem repeat sequences resembling the iteron structure of related plasmids were found. S1 endonuclease treatment and Southern blot analysis revealed that pMG1 accumulates single-stranded DNA (ssDNA) intermediate which indicates the rolling circle replication (RCR) mechanism of this plasmid. Homology search indicated that ORF II encodes plasmid mobilization protein and the presence of highly conserved oriT sequence in the upstream of this gene supported this assumption. RT-PCR showed that only ORF I is expressed in vivo. Based on these results pMG1 was exploited to construct a shuttle vector pBES2. It was successfully transformed into Bifidobacterium and maintained stably.
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