Influência de íons metálicos na formação de biofilme e aderência a células eucariontes em Escherichia coli enteroagregativa (EAEC)

Abstract

The metallic ions iron, cooper and zinc are essentials elements to survival of both microorganisms and hosts. To microorganisms, metallic ions take part of proteins structures and perform an important role in enzymatic activities as co-factors. However, these metals might also have a deleterious effect to cells, since in high concentrations they take part in free radical generation, act on peroxidation of membrane lipids and block action of fundamental enzymes to cellular metabolism. On a previous study, inhibition of iron capitation altered biofilm formation and adherence of enteroaggregative E. coli (EAEC) to epithelial cells. Hence, we decided to investigate the metallic ions influence in adherence of EAEC strains to biotic and abiotic surfaces. The strains used on this study had been already characterized regarding their fimbriae expression. Besides other characteristics, such as presence of iron capitation genes in strains, were considered when we evaluated the responses to metallic ions. Data showed that there is no parallel between these characteristics and the strains response to metallic ions. Nevertheless, results showed that metallic ions, especially cooper and zinc ions reduce biofilm formation in most of the tested strains. Additionally, other aspects like substrate influence biofilm formation. On this work, we observed that metallic ions interfere with biofilm formation in a distinguish way, there is a different response depending of the substrate, glass or polystyrene. We also tested if the presence of oxygen interfered with biofilm formation and it might increase or reduce biofilm in some of the strains. In addition, the strains showed increased or reduced hydrophobicity in the presence of metallic ions. Metals not only altered biofilm formation but also reduced cell viability on the biofilm. The cytotoxicity assays were performed in eukaryotic cells to verify the metals influence on cellular viability. Three cells lines were tested, HEp-2, T84 and Caco-2. The most resistant cell line, Caco-2, was chosen to adherence assays. We observed that metals modify the adherence pattern of some bacterial strains. In conclusion metallic ions interfere with EAEC pathogenesis, probably altering the surface of bacteria.