Transformation ofErwinia herbicolawith Plasmid pBR322 Deoxyribonucleic Acid

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Abstract
E. herbicola was transformed by a CaCl2 technique with plasmid pBR322 DNA at frequencies up to 1 .times. 10-6 transformants/recipient cell (TPR). Since pBR322 carries resistance to ampicillin (Apr) and tetracycline (Tcr), transformants were selected on media containing either one or both of those antibiotics. Covalently closed circular (CCC) plasmid DNA was isolated from lysates of E. herbicola (pBR322) transformants by equilibrium centrifugation in CsCl-ethidium bromide gradients. The CCC DNA of E. herbicola (pBR322) was found by EM and gel electrophoresis to contain a DNA species the same size as that of pBR322. This plasmid had the same restriction pattern as pBR322. Transformation of Escherichia coli with CCC DNA from E. herbicola/ pBR322 yielded Ap Tcr transformants at frequencies as high as 1 .times. 10-4 TPR. The CCC DNA isolated from all E. coli transformants tested had electrophoresis patterns identical to those of pBR322. Transformation of pBR322, a recombinant DNA cloning vehicle, into E. herbicola indicates that development of a gene cloning system in this species may be possible.