Adaptation of gut microorganisms to tannins

Tannin acid (TA) is a plant secondary metabolite (PSM) that is harmful to herbivores and limits herbivore nutrient utilization (antinutritional). The Qinghai voles living on the Qinghai-Tibetan Plateau eat large amounts of plants containing PSMs on a daily basis, however, there were fewer studies on how they adapt to high concentrations of PSMs. The aim of this study was to investigate how Qinghai voles regulate feeding strategies and gut microbes to adapt to different concentrations of TA. In this study, Qinghai voles were fed for 60 days with 0, 3%, 6% TA. We used hematoxylin-eosin staining for measurements of small intestinal villi and crypts; Gut microbes were profiled using 16S and meta-transcriptomic sequencing; and measured the level of SCFAs using high performance liquid chromatography. Our results reveled that the adaptive strategy of Qinghai voles to 3% TA was to increase food intake, and to 6% TA was to promote villus length and increase food intake. Gut microbes adapted to TA by increasing bacterial diversity and decreasing several gut bacterial succession rates, such as Cyanobacteria and Verrucomicrobia. And TA facilitated the creation of SCFAs. Moreover, TA inhibited alpha-mannosida,increased expression of tetracycline resistance genes and decreased expression of macrolide resistance genes,inhibited the expression of carbohydrate-active enzymes. This study revealed the mechanism of vertebrate adaptation to plant secondary metabolites.