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.