Nutritional immunity. Host's attempt to withold iron from microbial invaders

WITHIN the past half century, the doctrine of the biochemical unity of living matter has become well established. Metabolic pathways as well as methods of storage, transfer, and use of energy and of genetic information are found to have strong commonality in the cells of microorganisms, plants, and animals. As a consequence, similar kinds of organic and inorganic components are used in the building of protoplasm by the three forms of life. Moreover, the quantities of inorganic nutrilites needed for cell replication are quite similar. For example, to achieve maximal growth, cultures of cells of microorganisms, plants, and animals each require approximately 1μM solution of iron, 1 mM solution of phosphorus, and 1 mM solution of magnesium. Immunity In view of these similarities, it is remarkable that plants and animals have been able to develop, during evolution, methods for keeping many of their tissues and organs free of microbial invaders.