Characterization of three group A klebicin plasmids: localization of their E colicin immunity genes

We have investigated the immunity to E colicins conferred by three group A klebicin plasmids. pP5a, which encodes klebicin A1-P5, like pClo-DF13, confers immunity to colicin E6 on Escherichia coli K12, whilst pP5b and pP3, which encode klebicins A2-P5 and A3-P3 respectively, both confer immunity to colicin E3. We have determined the restriction endonuclease and functional maps of the three group A klebicin plasmids. By sub-cloning and transposon mutagenesis we have investigated the relationship between the klebicin immunity and the E colicin immunity conferred by these plasmids. The colicin E6 and the klebicin A1 immunity are encoded by a single gene present on pP5a. The colicin E3 and the klebicin A2 immunity are encoded by a single gene present on pP5b. The colicin E3 and the klebicin A3 immunity are encoded by separate genes present on pP3. Recombinant pML8412, which is derived from the ColE6-CT14 plasmid and encodes colicin E6 immunity, confers klebicin A1-P5 immunity upon Klebsiella pneumoniae UNF5023. Recombinant pKC23, which is derived from the ColE3-CA38 plasmid and confers colicin E3 immunity, confers immunity to klebicin A2-P5, but not to klebicin A3-P3.