Plasmid pSa causes loss of LPS -mediated adherence in Agrobacterium

1 Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60201, U.S.A. 2 Department of Microbiology and Immunology, Schools of Medicine and Dentistry, Oral Roberts University, Tulsa, Oklahoma 74171, U.S.A. 3 Department of Microbiology, Stritch School of Medicine, Loyola University, Maywood, Illinois 60153, U.S.A. ABSTRACT Summary: Suppression of virulence in Agrobacterium caused by introduction of the IncW R plasmid pSa into cells containing a Ti plasmid is accompanied by loss of site adherence in the pinto bean infection assay and by loss of site adherence on the part of LPS isolated from these strains. When cured of the pSa plasmid, infectivity and site adherence are restored. This indicates that LPS produced by pSa-containing agrobacteria is sufficiently modified that it will not support site adherence, the initial step of the infection process. Present address: Department of Microbiology, University of Sydney, Sydney, N.S.W. 2006, Australia.