X Wang

Inside every cell there are waste-recycling stations: lysosomes. To digest the trash, they need an acidic environment, and the acid is pumped in by a molecular pump called V-ATPase. With age this pump works more and more weakly, and lysosomes stop keeping up. But the bacteria living in the gut have their own building material, peptidoglycan, and as it turns out, it can serve as a key that restarts the pump.

An old mouse hangs on a wire two-thirds longer than a mouse its own age, and after running on a treadmill it doesn't collapse from exhaustion. The difference isn't training or diet: the mice had a single molecule suppressed, and their muscles worked like they did in youth. That molecule is microRNA-128-3p, a short chain of nucleotides that silences entire groups of genes.

Water in a sink spirals down the drain. A cell caught in the whirlpool of aging is much the same: it can no longer climb out, and every turn pulls it deeper. Scientists have found what sets this whirlpool spinning: the ApoD protein, which old cells release into their surroundings like a distress signal that actually drowns the neighbors.