FolM, a new chromosomally encoded dihydrofolate reductase in Escherichia coli

Escherichia coli (thyA DeltafolA) mutants are viable and can grow in minimal medium when supplemented with thymidine alone. Here we present evidence from in vivo and in vitro studies that the ydgB gene determines an alternative dihydrofolate reductase that is related to the trypanosomatid pteridine reductases. We propose to rename this gene folM.