Microbial antagonisms and antibiotic substances

On the basis of their relation to man, the microscopic forms of life may be classified in two major groups: pathogenic forms that attack living systems, especially those useful to man and to his domesticated plants and animals } and saprophytic forms that attack inanimate matter, in- cluding the universal scavengers and the organisms utilized in industry and in the preparation of foodstuffs. Between true parasitism-one or- ganism living in or upon the body of another-and true saprophytism -one organism merely destroying the waste products and the dead cells of another-are groups of relationships that may be designated as antagonistic and associative. In the first of these, one organism is injured or even destroyed by the other, whereas in the second, one or- ganism assists the other and may in turn be benefited by it.