PERTURBATION OF KEY COMPONENTS OF THE GUT-BRAIN-MICROBIOME AXIS BY THE PROTISTAN PARASITE BLASTOCYSTIS

Abstract

Blastocystis is a highly prevalent protistan parasite of the human gut that has been associated with disorders of intestinal inflammation and the gut microbiome. This thesis presents evidence that Blastocystis may have a greater ability to influence the human body than is currently understood, arguing that previously observed changes to the host gut are indicative of wider effects on a variety of host systems, including immunity, cognition, and mood. Such effects may play a role in existing neurological disorders. We characterize an aberrant tryptophan-producing Blastocystis enzyme, explore its behaviour in a physiological context, and demonstrate its ability to alter neurotransmitter metabolism and host behaviour in in vitro and in vivo models. These results establish a putative pathway to disease for Blastocystis, as well as demonstrating the potential for these parasites to influence the behaviour of their host.