Introduction to host microbiome symbiosis in health and disease

Abstract

Humans share a core intestinal microbiome and yet human microbiome differs by genes, species, enterotypes (ecology), and gene count (microbial diversity). Achievement of microbiota metagenomic analysis has revealed that the microbiome gene count is a key stratifier of health in several immune disorders and clinical conditions. We review here the progress of the metagenomic pipeline analysis, and how this has allowed us to define the host-microbe symbiosis associated with a healthy status. The link between host-microbe symbiosis disruption, the so-called dysbiosis and chronic diseases or iatrogenic conditions is highlighted. Finally, opportunities to use microbiota modulation, with specific nutrients and/or live microbes, as a target for personalized nutrition and therapy for the maintenance, preservation, or restoration of host-microbe symbiosis are discussed.

Fig. 1. Critical transition in chronic immune diseases (concept).

At baseline, in humans, eubiosis of the gut microbiota is associated with physiological immune tone (symbiosis—Homo sapiens “symbioticus”). Thereafter, genetic predisposition, infection, and modern changes in antibiotic use, diet, lifestyle, and environmental triggers lead to reversible imbalance of the gut microbiota and transient low-grade inflammation with a reciprocal impact on each other (crosstalk—Homo sapiens “modernicus”). Finally, exposure to stress signals above the system’s robustness can lead to a sustained alteration of the gut microbiota and inflammation (dysbiosis—Homo sapiens “dysbioticus”).

Fig. 2. Restoring symbiosis—from Homo dysbioticus to Homo symbioticus.

For restoration of the microbiota-host altered crosstalk, modification of nutrition can restore symbiosis. However, in case of microbiota-host sustained dysbiosis, restoration of symbiosis is more difficult and requires therapeutic intervention with microbiotherapy or fecal microbiota transplantation.