Immunoelectrophoretic comparison of cell envelope antigens in pathogenic and non-pathogenic Agrobacterium tumefaciens

The cell envelope antigens of a pathogenic strain (57P) of Agrobacterium tumefaciens were compared with those of a non-pathogenic strain (57sr) by means of quantitative Immunoelectrophoresis. Strain 57P was derived from 57sr by conjugative transfer of the tumour inducing (Ti) plasmid from strain B6Sm, and should differ from 57sr only with respect to characters encoded by the Ti plasmid. Both strains, when grown on glucose and (NH 4) 2SO 4, contained one cell envelope antigen (A) which was absent from 57P when grown on octopine as the sole carbon and nitrogen source. Another antigen (D) was present only in the pathogenic strain, when grown on octopine. Two more antigens (B and C) were restricted to the pathogen but were produced on both media. The possible identity of these antigens and their role in tumorigenesis is discussed.