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The species composition of the human intestinal microbiota differs between particle‐associated and liquid phase communities
Author(s) -
Walker Alan W.,
Duncan Sylvia H.,
Harmsen Hermie J. M.,
Holtrop Grietje,
Welling Gjalt W.,
Flint Harry J.
Publication year - 2008
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2008.01717.x
Subject(s) - biology , composition (language) , particle (ecology) , microbiome , ecology , microbiology and biotechnology , bioinformatics , philosophy , linguistics
Summary Many of the substrates available as energy sources for microorganisms in the human colon, including dietary plant fibre and secreted mucin, are insoluble. It seems likely that such insoluble substrates support a specialized microbiota, and in order to test this hypothesis, faecal samples from four healthy subjects were fractionated into insoluble (washed particulate) and liquid fractions. Analysis of 1252 PCR‐amplified 16S rRNA sequences revealed a significantly lower percentage of Bacteroidetes ( P = 0.021) and a significantly higher percentage of Firmicutes ( P = 0.029) among bacterial sequences amplified from particle‐associated (mean 76.8% Firmicutes, 18.5% Bacteroidetes ) compared with liquid phase (mean 65.8% Firmicutes, 28.5% Bacteroidetes ). Within the Firmicutes , the most significant association with solid particles was found for relatives of Ruminococcus ‐related clostridial cluster IV species that include Ruminococcus flavefaciens and R. bromii, which together accounted for 12.2% of particle‐associated, but only 3.3% of liquid phase, sequences. These findings were strongly supported by microscopy, using group‐specific FISH probes able to detect these species. This work suggests that the primary colonizers of insoluble substrates found in the gut are restricted to certain specialized groups of bacteria. The abundance of such primary degraders may often be underestimated because of the difficulty in recovering these bacteria and their nucleic acids from the insoluble substrate.