Digestive exophagy of bacterial biofilms by parasitic intestinal amoeba and its impact on stress tolerance, antibiotic resistance and cytotoxicity

The human protozoan parasiteEntamoeba histolyticais responsible for amebiasis, a disease endemic to developing countries.E. histolyticatrophozoites colonize the large intestine, primarily feeding on bacteria. However, in the GI, as well as in aquatic and soil microenvironments, bacterial cells form aggregates or structured communities, called biofilm, too large for phagocytosis. However, trophozoites are still able to invade and degrade bacteria under biofilm form by a mechanism mimicking digestive exophagy. E.histolytica cysteine proteinase degrade TasA, one of the main component of the biofilm matrix. Biofilm also play an important role protecting trophozoites against oxidative stress. The specific mechanism suggests that amoeba is adapted to biofilm predation and may serve as a new unexplored reservoir of novel therapeutic approaches to treat biofilms. Consistently, amoeba’s products restored antibiotic sensitivity to biofilm cells. Furthermore, our findings here show that probiotic biofilms may serve as a protective shield for mammalian cells, hindering the progression of the parasite towards them. Entamoeba histolytica trophzoites incubated with planktonic cell of B.subtilis, biofilm of B.subtilis or alone (control)