2.3 Growth curve measurement
Strains were inoculated with initial OD600 of 0.2 in Delft minimal medium, supplementing different concentrations of amino acids or nucleotide. Samples were taken at 0 h, 6 h, 12 h, 24 h, 36 h and 48 h, respectively, and the optical density was measured at 600 nm (OD600) by visible light spectrophotometer. Samples were diluted to OD600 = 0.2 - 0.8 for measurement, and OD600 values were calculated to demonstrate cell growth.