Summary
Over the past century, soybean oil (SBO) consumption in the United States increased 100,000%. The main SBO fatty acid, linoleic acid (18:2), inhibits the growth of lactobacilli in vitro. Human-associated lactobacilli have declined in prevalence in Western microbiomes, but how dietary changes may have impacted their ecology is unclear. Here, we compared the in vitro and in vivo effects of 18:2 on Lactobacillus reuteri and L. johnsonii. In vitro, directed evolution led to strong 18:2 resistance with mutations in genes for lipid biosynthesis, acid stress, and the cell membrane or wall. In murine, microbiomes conditioned on a high-18:2 diet yielded L. reuteri isolates with improved resistance. Small-intestinal Lactobacillus populations in vivo were unaffected by chronic and acute 18:2 exposure, yet harbored 18:2- sensitive strains. This work shows that small intestinal beneficial microbes are protected from toxic dietary components via the gut environment and their own capacity to evolve resistance.
Abbreviations
- LF
- low fat
- HF
- high fat
- SBO
- soybean oil
- FA
- fatty acid