thiK and thiL loci of Escherichia coli.

Mutants of Escherichia coli K-12 auxotrophic for thiamine phosphates were produced in stepwise fashion from the polyauxotrophic F- strain JC1552, via intermediate production of thiamine auxotrophs that had lost the enzymatic activity of either phosphomethylpyrimidine kinase or thiamine phosphate pyrophosphorylase. They include two types: one responds to thiamine monophosphate or thiamine pyrophosphate, and the other responds to thiamine pyrophosphate only; the former lacks thiamine kinase activity, and the latter lacks thiamine monophosphate kinase activity, in addition to the enzymatic defects caused by the first mutations. We found two genes, for which we propose the designations thiK and thiL, which govern the activities of thiamine kinase and thiamine monophosphate kinase, respectively. By conjugation and P1 transduction, the thiK locus was mapped at about 25 min, between pyrC and purB and close to fabD. The relative order of thiK with respect to nearby genes was tentatively established as pyrC-ptsG-fabD-thiK-purB. In the case of thiL, the locus was situated at about 9 min, between tsx and acrA and probably 0.2 min clockwise from the former.