Physiologically induced changes in the property of phenylalanine tRNA in Escherichia coli

Escherichia coli grown in a medium with less than 10⁻⁷ M-iron contain one or two abnormal species of phenylalanine tRNA. The abnormal phenylalanine tRNA species lack some of the chemical modifications of the normal phenylalanine tRNA. This deficiency in modification arises because an enzymic activity involved in the normal modification of phenylalanine tRNA is not present in cells grown at low iron concentrations. The same deficiency in modification of phenylalanine tRNA is observed also in bacteria grown under limiting aeration in an aged medium, in which most of the iron is present as an insoluble hydroxide. The abnormal phenylalanine tRNA species have the same chromatographic properties as methyl-deficient phenylalanine tRNA, but the bulk of the tRNA containing the abnormal phenylalanine tRNA is not methyl-deficient.