ABSTRACT
As currently defined, antibiotics are chemicals produced by microorganisms and which in low concentrations are capable of inhibiting the growth of, or killing, other microorganisms. Anti-microbial substances are also produced by higher plants and animals. Such substances are however excluded by this definition. Bacteriocins although produced by microorganisms are also not included in this definition because they are not only larger in molecular size than the usual antibiotics, but they are mainly protein in nature; furthermore they affect mainly organisms related to the producing organism. In comparison with bacteriocins, conventional antibiotics however are for more diverse in their chemical nature and attack organisms distantly related to themselves. Most importantly, while the information specifying the formation of ‘regular’ antibiotics is carried on several genes, that needed for bacteriocins being single proteins need single genes. It will be seen later that in the last few years this definition has been somewhat broadened by some authors to include materials produced by living things – plants, animals or microorganisms – which inhibit any cell activity.
