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J Bacteriol. 1973 December; 116(3): 1145-1149
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Loss of an Essential Function of Escherichia coli by Deletions in the thyA Region

^a Department of Biological Chemistry, The University of Michigan, Ann Arbor, Michigan 48104

ABSTRACT

In an attempt to obtain deletions in the thyA gene, an abnormal lysogen of having the prophage inserted between the thyA and lysA genes was induced, and the surviving cured cells were examined for Thy^– and Lys^– mutants. In nearly 10,000 cured cells, 184 Lys^– but no Thy^– mutants were found. At the same time, the induced phage contained an approximately equivalent number of thyA⁺ and lysA⁺ transducing particles. By contrast, in a strain with the genotype F' thyA^–lysA⁺/ thyA⁺lysA⁺, induction of the abnormal lysogen gave rise to many Thy^– mutants in the cells cured of the prophage. In these Thy^– mutants it was not possible to eliminate the episome with acridine orange, although the episome could be removed in control cultures with a thyA⁺ allele in the resident gene. Therefore, it was suggested that deletion of a gene in the region of the chromosome from the position of the insertion of the prophage through the thyA gene caused loss of an essential and diffusible function.

¹ Present address: Fermentation Research and Development, Upjohn Co., Kalamazoo, Mich. 49001.