Therefore, we here identified and characterized PSMs of S. xylosus, produced isogenic deletion mutants in the main detected psm genes, and used pure PSMs as well as supernatants of cultures of S. xylosus and its isogenic psm mutants to investigate the pathogenic potential of S. xylosus PSMs with a focus on AD pathogenesis. This evidence concerns the gene FOLH1 and Alzheimer disease.