Citrate utilizing ability linked to glutamic acid excretion governing conjugative plasmid in Klebsiella pneumoniae C3

Abstract

The citrate utilizing ability (Cit⁺) in Klebsiella pneumoniae C3 was simultaneously lost with the abilities to excrete glutamic acid and to biosynthesize proline. Both properties were proved to be plasmid determined (J. Jofre et al., J. Bact. 138, 721–725). Citrate utilization was transferred by conjugation from K. pneumoniae C3 to Escherichia coli K12. Moreover, the transfer of the ability to biosynthesize proline from strain C3 to well-characterized Pro- strains of E. coli established that loci proA and proB, but not proC, are complemented by the plasmid herein described. E. coli exconjugants transferred simultaneously the abilities to utilize citrate and to biosynthesize proline by conjugation to other E. coli strains. Plasmid DNA was detected in E. coli exconjugants either by cesium chloride-ethidium bromide ultracentrifugation or by agarose gel electrophoresis. Gel profiles established that a single plasmid of an estimated molecular weight of 57 megadaltons is present in all examined E. coli exconjugants. Pro₋E. coli were transformed to Pro⁺ Cit⁺ with plasmid DNA of exconjugants. Also, a Cit^-, Pro⁻ and non-glutamic acid excreting strain derived from C3 was rendered Cit⁺, Pro⁺ and glutamic acid excretor by transformation with plasmid DNA from E. coli exconjugants. Therefore it can be concluded that the three phenotypic characteristics above mentioned are complemented by a single conjugative plasmid.