Lambda transducing phages for the nalA gene of Escherichia coli and conditional lethal nalA mutations

Abstract

Defective λ transducing phages for the nalA region of the Escherichia coli chromosome were isolated from a lysogen in which λ is inserted in the nearby glpT gene. The three classes of transducing phages designated λnrdA, λdubiG, and λdnalA contained bacterial DNA extending from glpT through nrdA, ubiG, and nalA, respectively. The bacterial genes are in the left arm of the λ chromosome. Of the eleven polypeptides coded by λdnalA that were resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate only one was not also specified by λdubiG This 105,000 dalton polypeptide is the nalA gene product. The electrophoretic mobility and isoelectric point of this protein were unaffected by a nalA mutation (nalA48) that confers nalidixic acid resistance. Temperature-sensitive and amber mutations in the nalA gene were isolated using a λdnalA48 lysogen which is heterodiploid for nalA. The conditional lethality of these mutations proves that nalA is an essential locus.