On the origin of species: Factors shaping the establishment of infant's gut microbiota

Fetal, neonatal, and infant microbiome: Perturbations and subsequent effects on brain development and behavior

The human gastrointestinal tract harbors a diverse and complex community of microbes, termed gut microbiota, that normally assemble during the first postnatal years of life. This evolution-driven process has been shown to contribute to the developmental programming of epithelial barrier function, gut homeostasis, and angiogenesis, as well as the development and function of the immune system. Research over the last few years has revealed that the actions of the gut microbiota have much wider effects on host physiology and development than originally believed, including the modulation of brain development and behavior. This article briefly reviews recent findings on the impact of the gut microbiota on brain development, and how disturbances in the assembly and maturation of the gut microbiota may impact development of motor, social, and cognitive functions. The potential link between microbiota and metabolic requirements of the developing brain is also considered.

Secretory IgA in the Coordination of Establishment and Maintenance of the Microbiota

Starting at birth, the intestinal microbiota changes dramatically from a highly individual collection of microorganisms, dominated by comparably few species, to a mature, competitive, and diverse microbial community. Microbial colonization triggers and accompanies the maturation of the mucosal immune system and ultimately results in a mutually beneficial host-microbe interrelation in the healthy host. Here, we discuss the role of secretory immunoglobulin A (SIgA) during the establishment of the infant microbiota and life-long host-microbial homeostasis. We critically review the published literature on how SIgA affects the enteric microbiota and highlight the accessibility of the infant microbiota to therapeutic intervention.

Microbial perturbations and modulation in conditions associated with malnutrition and malabsorption

The intestinal microbiota is a complex ecosystem, which can be considered an accessory organ. It involves complex microbe-microbe and host-microbe interactions with indispensable functions for the human host with regard to the intestinal epithelium and barrier function, the innate and adaptive immune system, and its large metabolic capacity. Saccharolytic fermentation results in the production of short chain fatty acids, which exert an array of beneficial effects, while proteolytic fermentation leads to an increase in potentially harmful metabolites. In addition, numerous other microbial metabolites are being produced with various intestinal as well as extra-intestinal effects. Their generation depends on the composition of the microbiota as well as the availability of substrates, which both vary along the GI tract. Diet impacts the intestinal microbiota composition and activity in early infancy as well as in adults. Microbial perturbations have been demonstrated in subjects with under-nutrition and/or malabsorption. The bidirectional interactions between the microbiome, nutrient availability and GI function, can contribute to a vicious circle, further impairing health outcome in conditions associated with malnutrition and/or malabsorption. Integrated multivariate approaches are needed to further unravel the complex interaction between microbiome, diet and host factors, as well as possible modulation thereof by prebiotics or probiotics. The present overview will briefly outline the composition and function of the intestinal microbiota, its association with nutrient intake and availability, and will address the role of the intestinal microbiota in malnutrition and malabsorption.