Genetic control of basal level of alkaline phosphatase in Escherichia coli

Summary The basis for a difference in basal levels of alkaline phosphatase in two strains of E. coli has been examined. It was found that the enzyme level characteristic of a highlevel strain was not conferred upon a low level strain merely by the transfer of the pho ⁺, phoR⁺ or phoS ⁺ allele from the high-level strain to the low level strain. Such strains may have slightly altered basal levels of enzyme, but these changes are not quantitatively sufficient to account for the strain differences. Approximately 20% of the recombinants which receive the phoS ⁺ gene show a level of phosphatase intermediate between the high and low-level strains. The effect is specific for the basal level of phosphatase, since it does not affect the levels of three other enzymes, or the derepressed level of alkaline phosphatase itself. This latter fact is consistent with the view that the intermediate level strains have an intermediate level of repressor of alkaline phosphatase under repressed conditions. It is suggested that the basal level of enzyme is affected by several genes in addition to those previously described, and that the intermediate level strains have received the allele of one or more of these loci from the high level strain.