The remarkable complexity of the brain microbiome in health and disease

eToL profiling of control and Alzheimer’s disease (AD) human brain shows diverse microbes, with cingulate cortex having the highest burden and AD linked to over-represented pathogens.

• Why it matters: The brain microbiome’s composition and its possible relationship to neurodegenerative disease remain debated, especially which microbes differ between control and AD brain.
• What they did: Using electronic tree of life (eToL) small subunit rRNA probes, confirmed by large subunit rRNA analysis, the study surveyed control and AD brain microbes across regions (amygdala, cingulate cortex, hippocampus, hypothalamus) and individuals.
• The result: In AD brain, microbes were over-represented by two measures (normalized absolute microbe counts and specimen overabundance), including bacteria (Streptococcus; Staphylococcus/Bacillus; Sphingomonas/Ralstonia) and fungi (Aspergillus group; Candida group; Schizophyllum group; Cryptococcus group), with an uncharacterized chloroplastida more abundant.