STUDIES OF A PURINE-REQUIRING MUTANT STRAIN OF ESCHERICHIA COLI
Robert Guthrie
1949
Journal of Bacteriology
The production and isolation of mutant strains of Escherichia coli requiring for growth an exogenous source of an amino acid, B vitamin, purine, or pyrimidine have been reported by several investigators. The results have been summarized in a recent review (Tatum, 1946) . Such strains have been used recently for the assay of amino acids Lampen, Jones, and Perkins, 1947) . The present paper deals with a purine-requiring strain of E. coli, 9661-01, which was isolated following treatment with
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... iolet light. Under the conditions described herein, growth of this organism occurred only when any one of the purine bases, adenine, guanine, xanthine, or hypoxanthine, was present. Within limits, the amount of growth was related to the amount of purine added. Various purine bases have been described as either stimulatory substances or as essential growth substances for a number of bacteria (Peterson and Peterson, 1945) . Pappenheimer and Hottle (1940) have described a strain of group A hemolytic streptococcus with a requirement for purines that is qualitatively similar to that of E. coli 9661-01. Tatum (1946) has produced a mutant strain of E. coli with nitrogen mustard that requires purine. Any one of the four purine bases listed above is active. Mitchell and Houlahan (1946) have employed a mutant of the mold, Neurospora, for the bioassay of adenine plus hypoxanthine in tissue extracts. It is not intended in this report to propose the use of E. coli 9661-01 in the routine assay of purine bases. However, it is felt that the nature of the purine requirement of this organism appeared to be such as to warrant further investigation of its use for assay of natural materials for purine content. The stability of the requirement was such that little difficulty was encountered in maintaining this mutant strain in the laboratory. Studies of the conditions under which reversion to a purine-independent type occurs, are described. METHODS Isolation of organism. An arginine-requiring strain of E. coli ATC9661, isolated by Roepke, Libby, and Small (1944) , was used for the production of nutritionally deficient daughter strains. For the isolation of nutritional mutants from a suspension that had been irradiated with an ultraviolet germicidal lamp, the "layer-plate" technique of Lederberg and Tatum (1946) was employed. E. coli 9661-01, isolated in this manner, was found by a modification of the "auxanographic" plate method 39 on May 9, 2020 by guest http://jb.asm.org/ Downloaded from 1949]
doi:10.1128/jb.57.1.39-46.1949
fatcat:dq7nji6l6ncctnlapxbxdjag6u