Scope of bacterial surface effector molecules beyond probiotics

Probiotic has gained a lot of attention pertaining to their potential health benefits in the last decades. Moreover, the growing demands for probiotic-based dietary supplements, food products and pharmaceuticals, have further affirmed its role as a prophylactic and therapeutic agent. Although considered safe, the increasing incidence of allergic sensitization and autoimmune disorders further limits the use of live probiotics. Recent, mechanistic evaluation behind the probiotic benefits has unraveled the role of surface effector molecules as primary mediators of the probiotic action. This review initially introduces the structural-functional aspects of surface-associated molecules (surface proteins, cell-bound exopolysaccharide, lipoteichoic acid, pilli and peptidoglycan complex) of probiotic lactic acid bacteria involved in host-microbe interactions. Later, the recent findings involving the role of these effector molecules in various host-associated bio-functional attributes such as intestinal adhesion, immunomodulation, restoration of gut barrier integrity, anti-pathogenic and anti-biofilm, anti-oxidative, anti-tumor, anti-obesity, anti-diabetic potentials were discussed elaborately. Mostly, interactions of bacterial surface components with host-derived factors occur in the gastrointestinal tract which ensure the successful exertion of the beneficial effects of probiotic bacteria. Thus, the direct evidence of the applicability of the effector molecules in imparting bio-functional attributes possibly indicates a safer alternative to classical probiotics. Complete knowledge of chemical structures, targets and validated dosages of these natural molecules further expands the area of pharmabiotics.