Electron Microscopic Studies in Escherichia Coli on Mode of Action of Sodium Benzoate and Potassium Sorbate

Abstract

Traditionally food antimicrobials was utilized to extent the lag phase or inhibit the growth of microorganisms; however, it has been demonstrated that exposure to antimicrobials such as sodium benzoate and potassium sorbate in sublethal concentrations, and gradually increasing the dose, allowed the adaptation of microorganisms of interest in food, such as E. coli, exhibiting induced resistance by unknown mechanisms. Therefore, the objective of this study was to identify the ultrastructural changes in viable cells of E. coli adapted to high concentrations (7000 ppm) of these antimicrobials, using transmission electron microscopy (TEM). After treatment with potassium sorbate, E. coli presented important morphological changes such as the separation of the cell membrane from the cytoplasm and cell wall, the appearance of a remarkable electronic light at the center of cells containing condensed deoxyribonucleic acid (DNA) molecules, as well as the appearance of small dense granules of electrons. Therefores, potassium sorbate induced more severe shape structural changes, presence of unusual structures and loss of integrity compared to viable cells adapted to sodium benzoate.