Electron Microscopy of Disrupted Bacteria treated with Polymyxin E

SUMMARY: Mechanically disrupted cells of polymyxin E sensitive strains of Pseudomonas denitrificans and Escherichia coli and a resistant strain of Staphylococcus aureus were studied in the electron microscope. The occurrence of a secondary layer or membrane was observed within the outer cell walls derived from Ps. denitrificans and E. coli; a similar structure was not observed in cell walls prepared from Staph, aureus. Treatment of the disrupted cells of Ps. denitrificans and E. coli with polymyxin E resulted in marked morphological changes, whilst similar exposure of Staph. aureus cell walls to the antibiotic produced no significant changes in their morphology.