Differential partition of virulent Aeromonas salmonicida and attenuated derivatives possessing specific cell surface alterations in polymer aqueous-phase systems.

Two-polymer aqueous-phase systems were used to compare via partitioning the surface properties of strains of the fish pathogen Aeromonas salmonicida which differed in their ability to produce the surface protein array known as the A layer and in their ability to produce smooth lipopolysaccharide. In these two-phase systems, biological particles are known to partition between the phases in a manner related to a variety of surface properties, including hydrophobicity, charge, and lipid composition. Both the presence of the superficial protein layer and the O polysaccharide chains of lipopolysaccharide were shown to play an important role in the partitioning behavior of A. salmonicida cells. The presence of the A layer, which is crucial to the virulence of A. salmonicida, appeared to decrease the surface hydrophilicity of this pathogen and to increase, in a somewhat specific manner, its surface affinity for fatty acid esters of polyethylene glycol. The ability of two-polymer aqueous-phase systems to differentially partition A. salmonicida cells on the basis of differences in surface architecture suggests their general usefulness for the analysis of surface properties important in bacterial virulence and should permit their use in the selection of strains and mutants exhibiting specific surface characteristics.