it was found that : ( i ) the absence of one amino acid from the growth media had no effect on the plasmid copy number in prototrophic e. coli strains : ( ii ) the presence of only one amino acid in artificial media free of amino acids had a negligible effect on the plasmid copy number for the amino acids ala , arg , glu , his , leu , phe , thr , trp , and tyr : ( iii ) the combination of met and thr caused a rise in pbr322 plasmid copy number up to 90-100 plasmid copies per cell : ( iv ) the fe3+ concentration had an amplification effect on e. coli plasmids .
C0002520
amino acids
C0061472
glu