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Mutation in a Gene Required for Lipopolysaccharide and Enterobacterial Common Antigen Biosynthesis Affects Virulence in the Plant Pathogen Erwinia carotovora subsp. atroseptica

June 1999 , Volume 12 , Number  6
Pages  499 - 507

I. K. Toth , 2 C. J. Thorpe , 1 S. D. Bentley , 1 V. Mulholland , 1 L. J. Hyman , 2 M. C. M. Perombelon , 2 and G. P. C. Salmond 1

1Department of Biochemistry, University of Cambridge, Tennis Court Road, The Downing Site, Cambridge CB2 1QW, U.K.; 2Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K.

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Accepted 26 February 1999.

Spontaneous bacteriophage-resistant mutants of the phytopathogen Erwinia carotovora subsp. atroseptica (Eca) SCRI1043 were isolated and, out of 40, two were found to exhibit reduced virulence in planta. One of these mutants, A5/22, showed multiple cell surface defects including alterations in synthesis of outer membrane proteins, lipopolysaccharide (LPS), enterobacterial common antigen (ECA), and flagella. Mutant A5/22 also showed reduced synthesis of the exoenzymes pectate lyase (Pel) and cellulase (Cel), major virulence factors for this pathogen. Genetic analysis revealed the pronounced pleiotropic mutant phenotype to be due to a defect in a single gene (rffG) that, in Escherichia coli, is involved in the production of ECA. We also show that while other enteric bacteria possess duplicate homologues of this gene dedicated separately to synthesis of LPS and ECA, Eca has a single gene.

© 1999 The American Phytopathological Society