Graduate Student Literature Review: Significance of extracellular vesicles in the interaction between host and microbiota in the ruminant gastrointestinal tract

The gastrointestinal tract (GIT) plays a crucial role in maintaining overall health and performance in ruminants, with the rumen functioning as fermentation chamber for plant biomass. Intestinal epithelial cells are exposed to billions of microorganisms that significantly affect the epithelial barrier by activating complex metabolic and immune pathways. The interaction between microbiota and host is mediated by signaling compounds such as metabolites and peptides, and also extracellular vesicles (EV). The EV are small lipid membrane-bound vesicles released by almost all kinds of prokaryotic and eukaryotic cells in the GIT ecosystem, thus playing a role in intra- and interorganismic communication. They are unique among biological messenger molecules because of their structural, functional, and delivery characteristics. The EV carry various functional cargo, such as proteins, lipids, and nucleic acids, that modulate biological processes, including metabolism and immune functions. Their separation requires adequate protocols optimized for each biological matrix and subsequent confirmation of their identity in terms of size and the presence of specific marker proteins. For gaining insights into their functional role, omics technologies such as proteomics and transcriptomics are commonly used. Recent studies have shown the presence of EV in GIT compartments, including ruminal fluid and feces. These EV are produced not only by the host but also by the various types of microbiota residing in the different GIT sections. The EV can influence feed digestion, nutrient absorption, and overall performance and may also affect other organs such as liver, mammary gland and brain. The EV from ingested colostrum and milk are attributed with a special significance for intestinal function and development in early life. This review underscores the importance of further research to understand the complex roles of EV in the ruminant GIT.