Characterization of the E. coli K12 strain AB1157 as impaired in guanine/xanthine metabolism.

The widely used E. coli K12 strain AB1157 is impaired in guanine (xnathine) metabolism. Mutants blocked in purine biosynthesis before the stage of inosine monophosphate synthesis do not grow on external guanine or xanthine. The genetic nature of the Gua/Xan lesion is a deletion in the chromosome that covers the proA gene. The lesion causes reduced uptake of guanine.