Abstract
THE most striking reactions associated with the growth of micro-organisms are synthetic ones, particularly those concerned with protein synthesis. The synthesis of each compound is a stepwise process, each step being catalysed by an enzyme ; if the necessary enzyme is in some way inhibited or has been lost during evolution of the organism, then growth will be slowed down or stopped unless the product of the reaction in which that enzyme was involved is now provided in the external environment. When the synthesis of a compound essential for growth is impossible through natural loss of an enzyme system, then that compound becomes for the organism a ‘growth-factor'. By this term it is not meant to imply that the compound in question is not essential for those organisms which do not require it to be present in the external environment ; all growth-factors investigated have been shown to be synthesized by a wide variety of organisms which do not require them pre-formed and, where these are known, to have the same functions as in the more exacting organisms. Thus it seems justifiable to consider all growth-factors as ‘essential metabolites' and to regard the differences in requirements for them as differences in synthetic ability of the organisms investigated. On this basis, interference with the functioning or further utilization of the essential metabolite would produce the same metabolic lesion in those organisms which are able to synthesize it as already exists naturally in those which are not.
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Antibiotic Activity of Growth-Factor Analogues*. Nature 162, 356–359 (1948). https://doi.org/10.1038/162356a0
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DOI: https://doi.org/10.1038/162356a0