Bacterial hydrophobicity measured as partition of palmitic acid between the two immiscible phases of cell surface and buffer.

Bacterial hydrophobicity was measured as the affinity of palmitic acid to the cell surface. Cell surface and buffer were regarded as two immiscible phases with different affinity for the fatty acid. After equilibration of the system, the partition quotient (PQ) between the two phases was calculated. The bacteria hydrophobicity was expressed as the amount of cell mass required to give a partition quotient of 10 between amount of fatty acid bound to cell surface and amount of fatty acid in buffer (PQ 10). This system permits measurement of changes in hydrophobicity during bacterial growth as shown for Staphylococcus aureus, strain V 8. The hydrophobicity of this bacterium increased 4-5 times during the exponential growth-phase of the culture. In the stationary growth-phase there was a loss of hydrophobicity, which continued for at least 48 hours, linearly with time. The system was also tested with a Salmonella typhimurium strain and its rough mutant. The results were consistent with findings in other test systems measuring the hydrophobicity of these bacteria.