Mutations in two unlinked genes are required to produce asparagine auxotrophy in Escherichia coli

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Abstract
E. coli K -12 has 2 genes, asnA+ and asnB+, either one of which is able to satisfy the need of cells for asparagine. In order for a strain to have an auxotrophic requirement for asparagine, both genes must be mutationally inactivated. Mutants with [transposon] Tn5 inserted in asnB were obtained. asnB was mapped by conjugation and by 3 factor [phage] P1 transductions at 15 min on the E. coli K-12 linkage map, between ubiF and nagB. Specialized transducing phage .lambda.781 supE carried asnB, and supE, ubiF, nagA and nagB. asnA is the previously mapped ilv-linked asn locus, which is between uncB and rbs. E. coli C also has 2 asn genes, corresponding to asnA and asnB.