The Impact of Human Salivary Amylase Gene Copy Number and Starch on Oral Biofilms
2025
Dorothy K. Superdock | Lynn M. Johnson | Jennifer Ren | Alizeh Khan | Megan Eno | Shuai Man | Angela C. Poole
The copy number (CN) variant <i>AMY1</i> encodes the salivary amylase enzyme which promotes starch digestion. Although this gene has been associated with dental caries and periodontal disease susceptibility, the impact of the interaction between <i>AMY1</i> CN and starch on oral biofilms is unclear. We explored how oral microbiota communities shaped by <i>AMY1</i> CN respond to starch by employing an in vitro model of biofilm formation. We cultured biofilms using saliva samples from 31 donors with a range of <i>AMY1</i> CNs (between 2 and 20 copies) and self-reported gum disease states; we used media with and without starch. Many of the most prevalent genera in saliva were also prevalent in the derived biofilms. The presence of starch in the media was associated with lower biofilm alpha diversity. We found a significant interaction between <i>AMY1</i> CN and the media carbohydrate content that influenced the proportions of <i>Atopobium</i> and <i>Veillonella</i>. Members of these genera have been associated with dental caries and periodontitis. These findings suggest that the effects of carbohydrates on oral microbiome composition depend on <i>AMY1</i> CN and that human oral bacteria evolved in response to expansion of this host gene locus.
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