Abstract
The plasmid pBP11 has a size of 26,400 nucleotides and carries genes for resistance to ampicillin and sulfonamides but lacks Tra functions. By conjugational transfer it was derived from R-factor R1767, which confers multiresistance in Salmonella typhimurium. A physical map was constructed by employing restriction enzyme analysis combined with fragment cloning and characterization of homoduplex molecules in the electron microscope. pBP11 exhibits a symmetrical structure with unique and duplicated segments, the latter ones coding for resistance. Replication occurs in a unidirectional mode from three independent origins of replication. Multimeric forms of pBP11 were produced with a constant frequency—a process which appeared to be reversible and recA dependent. Formation of pBP11 and its multimerization by intra and intermolecular recombination is discussed.
Published Version
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