Bacteroidetes/Firmicutes Ratios in Mus musculus are Influenced by Saturation of Dietary Fatty Acids

T. Liu, H. Hougen, S. M. Hiebert, A. C. Vollmer

Author address: 

Swarthmore Coll., Swarthmore, PA.


Background: Mammalian gut microbes have been implicated in a variety of functions including the regulation of energy intake and storage, the control of immune system development and activity, and the synthesis of novel chemicals. Feeding mammalian hosts a high-fat diet shifts gut bacteria at the phylum level to reduce the ratio of Bacteroidetes to Firmicutes, while feeding hosts a fat-restricted diet increases this ratio. However, few studies have investigated the differential effects of different types of fatty acids on gut bacteria profile. Methods: Over a 10-week period, Mus musculus were fed a diet rich in omega-3 polyunsaturated fatty acids (n-3 PUFA), rich in omega-6 polyunstaurated fatty acids (n-6 PUFA), or rich in saturated fatty acids (SFA). Fecal pellets were collected before and after the 10-week treatment period from each of 12 mice (4 per treatment group). Bacterial DNA was extracted from the pellets and characterized by 16S rRNA analysis of the hypervariable V3 region. Bacterial DNA was cloned, sequenced, and classified to observe shifts in bacterial phylotypes as a result of differing dietary fatty acid content. Results: A nominal logistic regression model revealed a significant decrease in Bacteroidetes-to-Firmicutes ratio for mice receiving all three diets over the course of the treatment period, with a significantly greater decrease in mice on the SFA diet (79%) than in those on an n-3 or n-6 PUFA-rich diet (38% and 46%, respectively). Conclusion: High fat diets have been shown to shift gut bacterial profiles in mammals, and decreased Bacteroidetes-to-Firmicutes ratios have been correlated with obesity and increased adiposity. Our results suggest that different types of dietary fatty acids cause different shifts in gut microbial profiles, and that these different shifts may be a factor in the varying ways that fatty acids affect host health. Further investigations into the effects of fatty acid diets on gut microbiota gene expression, or on phylogenetic changes below the phylum level, may reveal more about the different effects of different fatty acids on gut microbes.

abstract No: 


Full conference title: 

110th General Meeting American Society for Microbiology
    • ASM 110th (2010)