The O-antigen lipopolysaccharide is the major barrier to plasmid DNA uptake by Klebsiella pneumoniae during transformation by electroporation and osmotic shock

Abstract Attempts to transform some wild-type strains of Klebsiella pneumoniae including recent clinical isolates, with plasmid DNA (pBR325) by electroporation and by osmotic shock were unsuccessful. However, derivatives of all the strains tested which lacked the O-antigen lipopolysaccharide were transformed with efficiencies approaching those obtained for Escherichia coli , that is > 10 5 -fold better than the parental strains. Loss of the K-antigen component had no significant effect upon transformation frequencies. The yields of transformants with a plasmid 10 times the size of pBR325 were only slightly less (approximately 30%).