Higher-level production of volatile fatty acids in vitro by chicken gut microbiotas than by human gut microbiotas as determined by functional analyses

Abstract

The aim of this study was to determine the relationship between the composition and function of gut microbiota. Here, we compared the bacterial compositions and fermentation metabolites of human and chicken gut microbiotas. Results generated by quantitative PCR (qPCR) and 454 pyrosequencing of the 16S rRNA gene V3 region showed the compositions of human and chicken microbiotas to be markedly different, with chicken cecal microbiotas displaying more diversity than human fecal microbiotas. The nutrient requirements of each microbiota growing under batch and chemostat conditions were analyzed. The results showed that chicken cecal microbiotas required simple sugars and peptides to maintain balanced growth in vitro but that human fecal microbiotas preferred polysaccharides and proteins. Chicken microbiotas also produced higher concentrations of volatile fatty acids than did human microbiotas. Our data suggest that the availability of different fermentable substrates in the chicken cecum, which exist due to the unique anatomical structure of the cecum, may provide an environment favorable to the nourishment of microbiotas suited to the production of the higher-energy metabolites required by the bird. Therefore, gut structure, nutrition, immunity, and life-style all contribute to the selection of an exclusive bacterial community that produces types of metabolites beneficial to the host.

Fig 1

Relative abundances of major bacterial groups in human and chicken microbiotas and their corresponding chemostat samples. Data are presented as the percentages of the total bacterial population made up by each bacterial group, as assessed by qPCR. The results are given as the means of measurements from three individual human (HU) and three chicken (CH) gut microbiotas and their chemostat products in VI (HFVI and CFVI) and VL (HFVL and CFVL) media.

Fig 2

Compositional comparison of human and chicken gut microbiotas grown in chemostats with two media. The percentage of sequences in each of the bacterial genera is shown according to pyrosequencing data assessed by RDP Classifier. The chicken microbiota (CH) and chemostat products in VI (CFVI) and VL (CFVL) media were compared to human microbiotas (HU) and their chemostat products in VI (HFVI) and VL (HFVL) media.

Fig 3

Compositions of uncultured bacteria in human and chicken gut microbiotas grown in chemostats with two media. The uncultured bacteria were defined according to criteria set up previously by Eckburg et al. (17). The percentage of uncultured bacteria in each of the bacterial genera was calculated according to the pyrosequencing data assessed by RDP Classifier. The chicken microbiota (CH) and chemostat products in VI (CFVI) and VL (CFVL) media were compared to the human microbiota (HU) and chemostat products in VI (HFVI) and VL (HFVL) media.