Surface charge and hydrophobicity of Salmonella, E. coli, Gonococci in relation to their tendency to associate with animal cells.

The surface charge and hydrophobicity of Salmonella typhimurium, Escherichia coli and Neisseria gonorrhoeae bacteria have been compared with their tendency to associate in vitro with human polymorphonuclear leucocytes (PMNL) and HeLa cells in culture. It was found that lipopolysaccharide mutations in S. typhimurium or E. coli, yielding core-defective mutants, increased the surface hydrophobicity, as assessed by aqueous two-phase partitioning and hydrophobic interaction chromatography, and promoted the association with PMNL and HeLa cells. The association to HeLa cells was much smaller for the E. coli than for the S. typhimurium bacteria. All the colonial variants of N. gonorrhoeae interacted significantly with the PMNL and the HeLa cells. They were liable to hydrophobic interaction. However, the non-piliated, T3 and T4, were slightly more hydrophobic, but less negatively charged, than the piliated T1 and T2 bacteria. There was a positive correlation between possession of COA- and pili-proteins in the outer membrane and enhanced interaction with PMNL. The reverse was found with respect to association with HeLa cells. The results support the hypothesis that expression of hydrophobicity and negative charge can increase the interaction of bacteria with certain animal cells, e.g. PMNL and HeLa cells.