MAPT and Alzheimer disease: Bacteria such as Helicobacter pylori, Borrelia burgdorferi, and Chlamydia pneumoniae have been implicated in AD susceptibility by promoting excessive phosphorylation of tau protein and elevating levels of pro-inflammatory bacteria (e.g., Escherichia/Shigella) while reducing levels of anti-inflammatory gut microbes (e.g., Ruminococcus) (Cryan et al., 2019; Murray et al., 2022).