Gut microbiome: between host genetics and environmental determinants

There are around 30,000 scientific papers on “human gut microbiome” found in PubMed but what defines a “healthy microbiome” is still not known. The large variability within individuals and across cohorts makes it very difficult to create such a reference. Only around 20% of the variance in the gut (fecal) microbiome can be explained. The host genome has a limited impact on bacterial diversity estimated from population and twin studies to account for less than 10% of the overall composition. Recently two prominent loci have been identified that consistently across various cohorts associate in particular with Bifibacteria in the stool. On the other side, hundreds of environmental and intrinsic factors (age, medications, disease states etc.) have been associated with microbiome diversity and changes in composition. The Bristol stool scale (colour and consistence of faeces) ranks amongst the most influential variables for composition and associates with the classified enterotypes. However, the stool features are mainly the result of the handling of intestinal contents in the large intestine and the transit time. Any alteration in gastrointestinal transit time (by means of pharmacological treatments for example) has been shown to affect feces composition (water content and microorganism mass) and is thus a major driver of microbiome composition and functionality.

What will I gain from watching this webinar?

• Understand how the overall bacterial mass relative to host body mass may be a critical factor when translating findings in rodents to the human condition
• Gain insight as to why microbiome research is largely ignoring key features of gut physiology
• Appreciate the caution needed in making scientific claims.