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

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 characteri stics of Escherichia coli in response to melatonin (100 nmol l(-1), 200 mu mol l(-1)) and to vitamin E (5 mg dl(-1)). A reduction was found in the sur face hydrophobicity of E. coli at concentrations of 200 mu mol l(-1) melato nin in a Mueller-Hinton (MH) broth. These effects were modified when a prot ein synthesis inhibitor (chloramphenicol) was added at sub-lethal concentra tions to the broth. Vitamin E produced a greater diminution in surface hydr ophobicity than melatonin. The adherence of E, coli to nitrocellulose filte rs 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 surf ace characteristics of E. coli, which could affect the micro-organism's cap acity to adhere to epithelia. Significance and Impact of the Study: We think that the oxide reduction pot ential of the host may be a determinant factor in the bacterial colonizatio n of animal tissue.