is the most common gastrointestinal protist found in humans and animals. Although the clinical significance of remains unclear, the organism is increasingly being viewed as a commensal member of the gut microbiome. However, its impact on the microbiome is still being debated. It is unclear whether promotes a healthy gut and microbiome directly or whether it is more likely to colonize and persist in a healthy gut environment. In healthy people, is frequently associated with increased bacterial diversity and significant differences in the gut microbiome. Based on current knowledge, it is not possible to determine whether differences in the gut microbiome are the cause or result of colonization. Although it is possible that some aspects of this eukaryote's role in the intestinal microbiome remain unknown and that its effects vary, possibly due to subtype and intra-subtype variations and immune modulation, more research is needed to characterize these mechanisms in greater detail. This review covers recent findings on the effects of in the gut microbiome and immune modulation, its impact on the microbiome in autoimmune diseases, whether has a role like bacteria in the gut-brain axis, and its relationship with probiotics.