Comparative study of the influence of melatonin and vitamin E on the surface characteristics of Escherichia coli

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Abstract
Aims: Melatonin is a hormone produced by the pineal gland and that affects the response of various cell membranes to an oxidative stimulus. Methods and Results: The present study evaluates the hydrophobic characteristics of Escherichia coli in response to melatonin (100 nmol l–1, 200 μmol l–1) and to vitamin E (5 mg dl−1). A reduction was found in the surface hydrophobicity of E. coli at concentrations of 200 μmol l–1 melatonin in a Müeller-Hinton (MH) broth. These effects were modified when a protein synthesis inhibitor (chloramphenicol) was added at sub-lethal concentrations to the broth. Vitamin E produced a greater diminution in surface hydrophobicity than melatonin. The adherence of E. coli to nitrocellulose filters increased in the presence of melatonin + chloramphenicol, and vitamin E. The effects observed were independent of the concentration of iron in the broth. Conclusions: Oxidative stress plays an important role in modifying the surface characteristics of E. coli, which could affect the micro-organism’s capacity to adhere to epithelia. Significance and Impact of the Study: We think that the oxide reduction potential of the host may be a determinant factor in the bacterial colonization of animal tissue.