Abstract
Experiments have shown that 0,02 M synthetic carbamyl phosphate inhibits the growth of Escherichia coli when added in the lag phase but not when added in the logarithmic: growth phase. Conversely, potassium cyanate at similar concentrations was found to cause only an elongation of the lag phase but when added during the logarithmic growth phase it was found to inhibit further growth of the cells. Both inhibitions were found reversible by addition of glutathione and cysteine. Carbamyl cysteine formation is offered as the possible explanation for the inhibitory property of carbamyl phosphate since the inhibition caused by carbamyl cysteine was also found to be reversible by additions of SH compounds and since carbamyl phosphate plus cysteine was found to produce carbamyl cysteine.