Gut bacterial surface polysaccharides

Gut bacterial surface polysaccharides are a diverse group of complex carbohydrates, including capsular polysaccharides (CPS), lipopolysaccharides (LPS), and exopolysaccharides (EPS), that form the outermost layer of bacteria residing in the human gastrointestinal tract [Raetz et al., 2002, Annual Review of Biochemistry]. These molecules act as the primary interface between the microbiome and the host, playing a dual role in both maintaining health and driving disease. For example, Polysaccharide A (PSA) from the symbiont Bacteroides fragilis is a well-characterized immunomodulator that promotes the expansion of regulatory T cells (Tregs) via TLR2 signaling, which helps prevent intestinal inflammation [Mazmanian et al., 2005, Cell; Round et al., 2009, Nature Reviews Immunology]. Conversely, the release of pro-inflammatory polysaccharides like LPS from Gram-negative bacteria can trigger systemic inflammation and metabolic endotoxemia through TLR4 activation [Coyne et al., 2008, Journal of Bacteriology]. In drug development, these polysaccharides are targeted to neutralize toxins, develop vaccines against enteric pathogens, or design postbiotics that mimic the beneficial effects of commensal bacteria. However, therapeutic manipulation of these targets must be carefully managed to avoid broad-spectrum disruption of the delicate gut ecosystem or the induction of severe inflammatory reactions.

Other names

Capsular polysaccharidesLipopolysaccharidesExopolysaccharidesBacterial glycansSurface antigensPeptidoglycanTeichoic acids

Neutralization of bacterial endotoxins and modulation of host immune signaling through Toll-like receptors (TLRs)