Location of purine genes on the physical map of Escherichia coli

Abstract

To locate the purine genes on the physical map of Escherichia coli (Table 1), strains mutant in purine pathway genes were obtained from B. Bachmann and made sensitive to bacteriophage X by P1 transduction to Mal+ where necessary. Genetic map positions were used to identify, for each gene, a group of phages among which one or more might be expected to carry complementing DNA. Samples of these phages were obtained from Y. Kohara, amplified by growth on the recD strain NM621 (6), and used in spot recombination-complementation tests both alone and in coinfections with wild-type X. One or more phages giving a positive spot test were identified for each of the 11 mutants, and the physical limits within which the gene must be located were derived. Restriction and/or sequence information was available for three of the genes, purE (2), purF (5), and purM (4), and was used to define physical gene locations further. The purF and purM restriction information from Tso et al. (5) and Smith and Daum (4), respectively, was in agreement with the information on the physical map, but the BglII restriction data for purE did not correspond. No attempt was made to compare the extensive restriction information for the DNA surrounding purE with the physical map.