Open Access Highly Accessed Research article

The Firmicutes/Bacteroidetes ratio of the human microbiota changes with age

D Mariat1*, O Firmesse1, F Levenez1, VD Guimarăes2, H Sokol13, J Doré1, G Corthier1 and J-P Furet1

Author Affiliations

1 INRA, U910, Unité d'Ecologie et du Système Digestif, Domaine de Vilvert, 78350 Jouy-en-Josas, France

2 INRA, UR496, Unité d'Immuno-Allergie Alimentaire, Domaine de Vilvert, 78350 Jouy-en-Josas, France

3 Service de Gastroentérologie et Nutrition, Hôpital Saint Antoine, AP-HP, Paris France

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BMC Microbiology 2009, 9:123  doi:10.1186/1471-2180-9-123

Published: 9 June 2009



In humans, the intestinal microbiota plays an important role in the maintenance of host health by providing energy, nutrients, and immunological protection. Applying current molecular methods is necessary to surmount the limitations of classical culturing techniques in order to obtain an accurate description of the microbiota composition.


Here we report on the comparative assessment of human fecal microbiota from three age-groups: infants, adults and the elderly. We demonstrate that the human intestinal microbiota undergoes maturation from birth to adulthood and is further altered with ageing. The counts of major bacterial groups Clostridium leptum, Clostridium coccoides, Bacteroidetes, Bifidobacterium, Lactobacillus and Escherichia coli were assessed by quantitative PCR (qPCR). By comparing species diversity profiles, we observed age-related changes in the human fecal microbiota. The microbiota of infants was generally characterized by low levels of total bacteria. C. leptum and C. coccoides species were highly represented in the microbiota of infants, while elderly subjects exhibited high levels of E. coli and Bacteroidetes. We observed that the ratio of Firmicutes to Bacteroidetes evolves during different life stages. For infants, adults and elderly individuals we measured ratios of 0.4, 10.9 and 0.6, respectively.


In this work we have confirmed that qPCR is a powerful technique in studying the diverse and complex fecal microbiota. Our work demonstrates that the fecal microbiota composition evolves throughout life, from early childhood to old age.