Differential Growth Patterns of Escherichia Coli Mutants with Ribothymidine Deficient Transfer Ribonucleic Acid: Study of Selected Biochemical Parameters
Forsberg, Erik J.
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An Escherichia coli K12 mutant lacking 5-methyluridine in its transfer ribonucleic acid (tRNA) was shown to have a lag phase in growth about five hours longer than the lag phase of the parental strain whose tRNA contained this naturally occurring modified nucleoside when both strains were grown in a mimimal salts/glucose medium supplemented with threonine, histidine, leucine, arginine, and thiamine. The addition of valine and isoleucine to this medium reduced the difference in the lag phases between the mutant and parental strains by three hours with littIe effect on the parental strain itself. The concentration of free valine was slightly reduced in the mutant strain as compared to the parental strain, both harvested during the stationary phase of growth. During the lag phase of growth, isoleucine concentration was slightly reduced in the mutant strain. However, these differences in valine and isoleucine concentrations between the two strains are probably insignificant. The percentage of tRN Val aminoacylated in vivo was similar in both strains at about 55%. The percentage of tRNA Arg aminoacylated in vivo was also similar in both strains at about 99%. The percentage of tRNA Ile aminocaylated appeared to be considerably reduced in the mutant strian, suggesting an effect of the lacking 5-methyluridine residue on the aminoacylation of tRNA Ile. The results. are, however, questionsble and further experimentation is necessary.