Effect of chitosan on membrane permeability and cell morphology of Pseudomonas aeruginosa and Staphyloccocus aureus

The mechanism of action of over 85% deacetylated chitosan on Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus was investigated. Results showed that after treated with chitosan, the electric conductivity of bacteria suspensions increased, followed by increasing of the units of average release for alkaline phosphatase (ALP) and glucose-6-phosphate dehydrogenase (G6PDH). SDS-PAGE and agarose gel electrophoresis indicated that the soluble proteins and intact DNAs decreased or disappeared in chitosan-treated bacteria cells, demonstrating that chitosan performed its antibacterial function via increasing the permeability of cell membranes. Moreover, chitosan had a stronger effect on the cell membrane of S. aureus than on that of P. aeruginosa due to the differences in their cell structures. Transmission electron microscopy (TEM) observations further verified that S. aureus is more sensitive than P. aeruginosa to chitosan. Our works provide additional evidences in support of chitosan being regarded as a natural bactericide.