The dgt gene of Escherichia coli facilitates thymine utilization in thymine-requiring strains

Improved Method for the Isolation of Thymine-requiring Mutants of Escherichia Coli.

Thymine-requiring mutants of Escherichia coli were rarely found before the observation by Okada, Yanagisawa, and Ryan (Z. Vererbungslehre 92:403, 1961) that cultures of bacteria grown in the presence of high concentrations of aminopterin, thymine, purines, and serine contain a surprising number of cells unable to synthesize their own supply of thymine. They showed that these thymine-dependent m...

Loss of deoxyribonucleic acid-thymine during thymine starvation of Escherichia coli.

A substantial loss of deoxyribonucleic acid-thymine occurs during thymine starvation of several thymine auxotrophs derived from Escherichia coli strains B, 15, and K-12.

Technique for starvation of Escherichia coli of thymine.

YjjG, a dUMP phosphatase, is critical for thymine utilization by Escherichia coli K-12.

Exogenous thymine must be converted to thymidine to enable a thyA (thymidylate synthase) mutant to grow. The deoxyribose in the thymidine comes from dUMP, which must first be dephosphorylated. The nucleotidase YjjG is critical for this step. A yjjG thyA mutant cannot use thymine for growth on a glucose minimal medium.

The thymine-thymine pyrimidine-pyrimidone(6-4) ultraviolet light photoproduct is highly mutagenic and specifically induces 3' thymine-to-cytosine transitions in Escherichia coli.

We have constructed single-stranded, M13-based vectors that contain a specifically located thymine-thymine pyrimidine-pyrimidone(6-4) UV photoproduct and have used these to estimate the frequency and accuracy of DNA replication past this adduct in uvrA6 cells of Escherichia coli. Both the normal and the Dewar valence photoisomer of the (6-4) adduct were studied. In the absence of SOS induction,...