Aging-related changes of the microbiome

• expands our digestivecapacity

• produces essentialnutrients

• increases colonizationresistance againstpathogenic intruders

• assists in the detoxificationof xenobiotics

prevalent microbiota composition configurations in gut microbiome space

• Bacteroides 1

• Bacteroides 2

• Prevotella

• Ruminococcaceae

• The colon is an open system

• System dilution rates/transit times impose bacterial growth rates to avoid wash-out/egestion

• Sample average maximum growth potentials correlate with stool consistency in R/B enterotypes

• P samples – alternative strategies to avoid wash-out (attachment tohost tissues, specific substrate

requirements)

—> Slow transit, increased proteolytic fermentation

Stool consistency is associated with microbiota richness and enterotypes

—> R enterotype – high richness – hard stools

—> R enterotype – high richness – hard stools – slow growth – proteolytic fermentation – slow transit – high microbial load

• diet

• drugs (antibiotics, laxatives, but also non-antibiotic drugs)

• data are compositional

• high inter-individual variance

• cell counts can differ

• relative data show negative correlation bias —> quantitative analyses better

Dysbiosis of the gut microbiota: an ecosystem that fails to perform its commensal role and contributes to disease onset or progression by increasing host susceptibility toward disease

development or by (co-)initiating or sustaining physiological responses affecting host health.

Bact2: disease-associated low cell count enterotype

• increased moisture and inflammation

• Low microbial density

• Low species/functional diversity

• Low functional redundancy

• Low abundances of health associated bacteria (e.g. butyrate producers)

—> is linked to lower quality of life & depression

—> Prevalence of Bact2 increases with BMI

—> increased richness (decrease of colonic motility —> higher transit times)

—> decreased core microbiota