EFFECT OF O-METHYL-DL-THREONINE AND O-METHYL-DL-SERINE ON GROWTH AND PROTEIN SYNTHESIS IN ESCHERICHIA COLI.

Neale, S. (Department of Botany, University College, London, England), and H. Tristram. Effect of O-methyl-dl-threonine and O-methyl-dl-serine on growth and protein synthesis in Escherichia coli. J. Bacteriol. 86:1241-1250. 1963.-Addition of either O-methyl-dl-threonine or O-methyl-dl-serine to exponentially growing cultures of Escherichia coli resulted in "linear" increases in optical density. The total cell count, however, remained constant, the increase in optical density being accompanied by a marked increase in cell length. In the presence of O-methyl-dl-serine, a phase of "linear" growth was followed by exponential growth, which was maintained during a second passage through analogue-containing medium but not after a subsequent passage through normal medium, suggesting phenotypic adaptation to the analogue. The differential rate of incorporation of amino acids into trichloroacetic acid-insoluble material was unaffected by growth in the presence of either O-methyl-dl-threonine or O-methyl-dl-serine. Neither analogue was incorporated into E. coli protein. The effect of the analogues on the production of alkaline phosphatase and beta-galactosidase was examined. The precise point and mode of action of the analogues have not been determined, but available evidence suggests that the growth-inhibitory effects of both substances are due to interference with the biosynthesis of threonine and methionine.