Composition, variability, and temporal stability of the intestinal microbiota of the elderly

Abstract

Alterations in the human intestinal microbiota are linked to conditions including inflammatory bowel disease, irritable bowel syndrome, and obesity. The microbiota also undergoes substantial changes at the extremes of life, in infants and older people, the ramifications of which are still being explored. We applied pyrosequencing of over 40,000 16S rRNA gene V4 region amplicons per subject to characterize the fecal microbiota in 161 subjects aged 65 y and older and 9 younger control subjects. The microbiota of each individual subject constituted a unique profile that was separable from all others. In 68% of the individuals, the microbiota was dominated by phylum Bacteroides, with an average proportion of 57% across all 161 baseline samples. Phylum Firmicutes had an average proportion of 40%. The proportions of some phyla and genera associated with disease or health also varied dramatically, including Proteobacteria, Actinobacteria, and Faecalibacteria. The core microbiota of elderly subjects was distinct from that previously established for younger adults, with a greater proportion of Bacteroides spp. and distinct abundance patterns of Clostridium groups. Analyses of 26 fecal microbiota datasets from 3-month follow-up samples indicated that in 85% of the subjects, the microbiota composition was more like the corresponding time-0 sample than any other dataset. We conclude that the fecal microbiota of the elderly shows temporal stability over limited time in the majority of subjects but is characterized by unusual phylum proportions and extreme variability.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Aggregate microbiota composition at phylum level in (A) 187 (161 time-0 and 26 time 3-mo) fecal samples from elderly subjects, (B) 9 healthy younger adult controls, and (C) at genus level in the 187 fecal samples from elderly subjects (the smaller pie chart to right is inserted for clarity). Only major taxonomic groups are shown; these cover 95% of all reads assigned to genus level.

Fig. 2.

Interindividual variation in the proportion of major phyla (A), Clostridium clusters (B), and the genera Faecalibacterium and Ruminococcus (C) in 187 fecal samples from elderly subjects. Only the seven largest phyla are shown in A. Samples are ordered, from left, according to their Bacteroidetes proportion (A), cluster IV proportion of all reads assigned to Clostridium clusters (B), and Faecalibacterium proportion (C) to illustrate the dramatic interindividual variation.

Fig. 3.

(A) The core fecal microbiota of elderly subjects at the levels of phylum, genus and Clostridium cluster compared with similarly defined core microbiota from four studies of younger adults and nine young adult controls. (B) Unique microbiota defined by comparing elderly and younger adults (published datasets). (C) Unique microbiota defined by comparing elderly and younger adults (this study).

Fig. 4.

Variation in the microbiota between time-0 and time 3-mo samples from 26 subjects. Mean (± SEM) unweighted and weighted UniFrac distances between the samples as indicated.