Every cell has waste-processing plants called lysosomes. For them to work, the inside has to be acidic. A special pump delivers that acid, but with age it weakens, and the cell does a worse job of clearing out trash. The bacteria living in the gut have a tough shell: the cell wall. When this wall breaks down, it yields small fragments called peptidoglycan. And these fragments act like a key, switching the pump back on.
So the researchers added purified peptidoglycan to the food of worms and mice. The worms began to live on average 10% longer, and the mice roughly 10% longer, and the old animals improved in mobility and appearance. It turned out that the bacterial wall fragments get inside cells, find the lysosomes and switch the pump on directly. The lysosomes become more acidic and digest trash better. When the pump was deliberately blocked, the effect vanished.
This discovery matters because no natural substance capable of switching this pump on directly was known before. Now it is clear that gut bacteria do more than help digest food: they also leave keys in our cells that keep things in order. Perhaps one day a supplement made from bacterial wall fragments will help cells stay clean and healthy for longer.
Peptidoglycan is the very molecule that makes up the bacterial cell wall, and it is what our innate immune receptors recognize to trigger inflammation. Now it turns out that the same molecule can act as a molecular tonic for lysosomes.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.