Commensal intestinal protozoa: an update on their role in the intestinal microbiota

Abstract

The intestinal microbiota constitutes a complex ecosystem composed of bacteria, fungi, and parasites that symbiotically inhabit the human intestine and participate in metabolic and immunological processes that contribute to the maintenance of homeostasis. In contrast, when dysbiosis occurs, it appears to be associated with various diseases. Recent research has shown that some species of commensal protozoa may have a beneficial influence on intestinal health. Studies conducted in humans have indicated that species such as Entamoeba dispar do not alter the composition of the microbiota. Conversely, Entamoeba hartmanni, Entamoeba moshkovskii, Entamoeba coli, and Endolimax nana have demonstrated a possible beneficial role by promoting the proliferation of bacteria such as Coprococcus, Akkermansia, and Alistipes, as well as the production of short-chain fatty acids, which have been associated with a healthier microbiota. In contrast, Pentatrichomonas hominis and some subtypes of Blastocystis spp. appear to be linked to a possible reduction of protective bacteria. Nevertheless, species such as Chilomastix mesnili, Entamoeba polecki, and Retortamonas intestinalis lack sufficient research to establish their role in the human microbiota. This study highlights the importance of research to better understand the interaction between protozoa and the human microbiota.