We speculate that it may be significant that the first Gram-negative anaerobic bacterial species intensively studied as a potential contributor to the onset of Alzheimer's disease (AD), that being the bacillus Bacteroides fragilis appears to utilize damaged or leaky physiological barriers and an activated NF-kB (p50-p65) - pro-inflammatory miRNA-146a-miRNA-155 signaling circuit to convey microbiome-derived pathogenic signals into the brain.