Introduction
The microbiota encompasses a wide range of beneficial bacteria that coexist within the human gastrointestinal (GI) system. These symbiotic microorganisms play a crucial role in maintaining the overall health and wellness of the human body, aiding in digestion, nutrient absorption, and immune system regulation1. The study of gut microbiota has increasingly gained attention, particularly in the last two decades. Over time, the terms microbiota and microbiome have been used interchangeably. In this article, we use microbiota to refer to bacterial taxa and microbiome to refer to microbial genome2.
The human microbiota has a complex network of diverse microbes, including bacteria, fungi, protozoa, archaea, and viruses3-5. Through symbiosis, microbiota plays central roles in protection against enteric pathogens, maturation and homeostasis of the immune system, regulation of the immune response, energy metabolism, and production of essential nutrients6-9. On the other hand, dysbiosis of the microbiota is associated with numerous conditions, including IBDs, antibiotic therapy-related colitis, and colonic cancer (Table 1)2,10-13.
Glycans and glycoconjugates (i.e., glycoproteins, glycolipids, proteoglycans, etc.) are found in all living organisms and displayed in diverse and distinct structures, combinations and sizes14. They play essential roles in cell signaling, energy metabolism, and structural support15. At the GI tract, glycans are primarily found on mucin glycoproteins and dietary fibers, both metabolized by the gut microbiota15-17. Therefore, by gaining a deeper comprehension of the relationship between the gut microbiota and host/dietary glycans, we can pinpoint the root pathophysiologic mechanisms of diseases associated with the dysbiosis of the gut microbiota.
This review discusses the complexity and function of gut microbiota from a bacterial perspective. We explore how various elements like the gut microbiota, gut epithelial barrier, and immune cells work together to regulate gut immunity to establish and maintain a homeostatic environment. We also examine the significance of glycan and mucus metabolism in this process. Lastly, we explore different modulatory approaches for maintaining and restoring functional microbiota in the GI tract.