Parabacteroides goldsteinii

^[1]^[2]

Epidemiology

gram-negative, obligately anaerobic bacterium
- outer membrane containing lipopolysaccharide
non-spore-forming, non-motile, rod-shaped bacterium

gut bacteria that proliferates as mice
plays a role in cognitive decline in mice [2
- interferes with signalling along sensory nerves that connect the gut to the brain
  - results in a decline in sensory perception of the external world
  - produces high amounts of medium-chain fatty acids that trigger release of inflammatory molecules including IL-1 beta through activation of GPR84 on the cell surface ofmyeloid cells/macrophages
    - IL-1 beta receptor on neurons that express PHOX2B mediates memory impairment
    - vagus neuron activation counters IL-1 beta induced cognitive decline
  - the inflammatory molecules released by macrophages suppress signalling along the vagus nerve
Parabacteroides goldsteinii blocks communication between the gut & the brain leading to cognitive decline

↑ Wikipedia: Parabacteroides goldsteinii https://en.wikipedia.org/wiki/Parabacteroides_goldsteinii
↑ Chen E Memory loss is fuelled by gut microbes in ageing mice. If confirmed in people, the finding might lead to gut-targeted therapies that could reverse cognitive decline. Nature News. March 11, 2026 https://www.nature.com/articles/d41586-026-00768-6
Cheng YT, Mazmanian SK Gut microbes affect cognition during ageing. As mice age, changes in the microorganisms in their guts contribute to cognitive decline by altering signalling between the gut and brain. Nature News & Views. March 11, 2026 https://www.nature.com/articles/d41586-026-00492-1
Cox TO, Devason AS, de Araujo A et al Intestinal interoceptive dysfunction drives age-associated cognitive decline. Nature. 2026 Mar 11. PMID: https://pubmed.ncbi.nlm.nih.gov/41813891 https://www.nature.com/articles/s41586-026-10191-6