AFTER decades of disappointment, we may have a new lead on fighting Alzheimer’s disease. Compelling evidence that the condition is caused by a bacterium involved in gum disease could prove a game-changer... Now researchers from Cortexyme and several universities have reported finding the two toxic enzymes that P. gingivalis uses to feed on human tissue in 99 and 96 per cent of 54 human Alzheimer’s brain samples taken from the hippocampus – a brain area important for memory (Science Advances, doi.org/gftvdt). These protein-degrading enzymes are called gingipains, and they were found in higher levels in brain tissue that also had...