THE CHANGES IN THE SURFACE CHARACTERISTICS OF PSEUDOMONAS-SYRINGAE INDUCED BY A PLASMID

The changes in the sedimentation, the surface properties, and the attachment of Pseudomonas syringae pv. atropurpurea NIAES 1309 induced by introduction of the plasmid pBPW1=Tn7 were studied by comparing wild-type (WT) cells and cells containing the plasmid (pBPW1 cells). The cell sedimentation rate, which was markedly enhanced by the introduction of the plasmid, was investigated quantitatively by using an image analyzer. The element causing the sedimentation was assumed to exist at the cell surface. The pBPW1 cells showed a greater negative surface charge than the WT cells. Infrared spectra together with the data of the cell surface charge suggested that the pBPW1 cells contained more protein but less sugar residues at the cell surface compared with WT cells. Little difference could be found in the surface free energy, based on dispersion and polar components, between WT and pBPW1 cells. Microbial cell attachment to the surface of glass was observed continuously in a parallel plate flow system. The number of pBPW1 cells attached to the glass surface was greater than that of the WT cells: about 5 times greater after 6h from the beginning of the experiment. A factor other than the surface charge was assumed to be responsible for the cell sedimentation and/or the cell attachment to the glass surface.