A mutant of Escherichia coli K-12 that is defective in the synthesis of 5-methyluridine (ribothymidine) in tRNA was used to identify precursors to phage T4-specific tRNA. The precursor molecules, isolated by gel filtration, were more than twice the size of tRNA. This method is suitable for isolation of rather large amounts of such precursor molecules.
Coliphages Escherichia coli