This study investigated how Polysorbate 80, a non-ionic surface-active agent, affects cell permeability and viability of Pseudomonas aeruginosa under environmental stress. Researchers measured leakage of 260 nm-absorbing cellular constituents (nucleotides), uptake of fluorescent dye, and bacterial survival when exposed to rapid changes in pH, temperature, and salt concentration. Polysorbate 80 enhanced leakage maximally at 0.125% concentration across multiple temperatures and bacterial cell densities, and this effect was consistent across three P. aeruginosa strains but not E. coli. Increased salt concentration in the suspension medium reduced leakage. Bacteria previously exposed to Polysorbate 80 showed greater viability losses when suddenly transferred to solutions with different osmotic properties, pH, or temperature. The leakage and viability loss were not directly correlated; instead, viability loss correlated with the magnitude of sudden environmental change. The data support the hypothesis that Polysorbate 80 directly and immediately alters the bacterial cell membrane's permeability barrier through physical interaction, likely disrupting membrane molecular organization in these Gram-negative organisms.

Key findings

• Polysorbate 80 caused maximum cell leakage at 0.125% concentration, consistent across temperatures (4°C, 18°C, 37°C) and three P. aeruginosa strains, but showed different patterns in E. coli
• Polysorbate 80 was rapidly taken up by bacteria (complete within 5 minutes) and increased uptake of the fluorescent dye ANS into cells
• Bacteria exposed to Polysorbate 80 experienced greater viability losses when subjected to sudden changes in pH, temperature, or salt concentration compared to unexposed controls
• Increased NaCl concentration in suspension medium progressively reduced both leakage and viability loss, suggesting osmotic protection
• No direct correlation existed between degree of constituent leakage and viability loss; instead, viability loss correlated with the magnitude of sudden environmental change