Examination of DNA from 21 primate species – from squirrel monkeys to humans – exposes an evolutionary war against infectious bacteria over iron that circulates in the host’s bloodstream. Supported by experimental evidence, these findings, published in Science, demonstrate the vital importance of an increasingly appreciated defensive strategy called nutritional immunity.
When bacteria that cause infectious diseases invade, the host starves the bacteria by hiding circulating iron, an essential nutrient it needs for survival, within the folds of a protein called transferrin. LEFT – When the bacterial protein, TbpA, grasps hold of the primate protein, transferrin, it can steal transferrin’s iron. CENTER – Over evolutionary time, transferrin has evolved mutations (green circles, green arrow points to most recent mutation) that allow transferrin to evade TbpA. RIGHT – TbpA, in turn, has evolved mutations (blue circles, blue arrows points to most recent mutation) that again enable it to grasp hold of transferrin and steal it’s iron. The evolutionary arms race has lasted 40 million years, highlighting the importance of the primate defense mechanism, called nutritional immunity, in the conflict between host and bacterial pathogen.
Credit: Janet Iwasa, Ph.D., University of Utah