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J Bacteriol. 1973 April; 114(1): 96-102
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Isolation and Properties of a Ribonuclease-Deficient Mutant of Salmonella typhimurium

^a Department of Bacteriology, University of California, Davis, California 95616

ABSTRACT

A mutant of Salmonella typhimurium has been isolated that has less than 5% of the ribonuclease activity of the parent strain. Mutant screening and enzyme assays were done in the presence of ethylenediaminetetraacetic acid, a substance that activates ribonuclease I and inhibits other known microbial nucleases. Genetic mapping indicates that the mutation is located between the purE and gal genes on the Salmonella chromosome. A ribonuclease-deficient mutant that carries a deletion in the pyrF gene is unable to utilize ribonucleic acid as a pyrimidine source, whereas the pyrF parent with normal ribonuclease activity will grow. This suggests that the enzyme may perform a scavenge function in the utilization of exogenous ribonucleic acid. Loss of this enzyme seems to have no detrimental effects on the growth of Salmonella.

¹ Present address: Virus Laboratory, University of California, Berkeley, Calif. 94720.