Bacterial Antagonism between Bacterium Coli and Common Intestinal Pathogens

In any medium, pure cultures of microbes are free from associative and competitive effects of other microbes as happens in a mixed culture. When two organisms are capable of utilising the same nutrients but are differently affected by environmental conditions such as reaction of the medium, air supply, temperature, etc., the one that finds condition more suitable for its development will grow more.rapidly and in time may be able to suppress the other. On the other hand, when two or more organisms live in close proximity, they may exert antagonistic, indifferent or favourable effects upon one another. The three important types of antagonisms are (a) repressive, inhibitory or bacteriostatic, (6) bactericidal, (c) bacteriolytic. Different organisms possess different degrees as well as different mechanisms of antagonism; some act directly, and some passively by causing change of Ph of the medium or impoverishment of some of the nutrient constituents of the medium. Though microbial antagonism can be looked upon largely as a result of series of physical factors, in most cases it can be explained by the production of toxic substances bv the antagonist. (Waksman, 1945).