This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Barnes, M. H. Articles by Rownd, R. Search for Related Content PubMed PubMed Citation Articles by Barnes, M. H. Articles by Rownd, R.

 Previous Article  |  Next Article 

J Bacteriol. 1972 September; 111(3): 750-757
Copyright © 1972 American Society for Microbiology. All Rights Reserved.

Effect of Thymine Limitation on Chromosomal Deoxyribonucleic Acid Synthesis in Proteus mirabilis

Laboratory of Molecular Biology and Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706

ABSTRACT

The effects of thymine limitation on the rates of growth, deoxyribonucleic acid (DNA) synthesis, and increase in viable cell number for a thymine auxotroph of Proteus mirabilis were investigated. At thymine concentrations of 1.0 µg/ml and below, these rates were markedly decreased. After a reduction in thymine concentration from 10 µg/ml to 0.2 µg/ml, mass synthesis continued at the preshift rate for several hours. In contrast, the rate of DNA synthesis immediately decreased, resulting in a decrease in the DNA to mass ratio to about one-half of its normal level. Viable counts remained constant for several hours after the reduction in thymine concentration, and enlarged cells and multicellular "snakes" were formed. The rate of DNA synthesis was reduced at thymine concentrations below approximately 1.7 µg/ml. The addition of thymine to cultures which had been completely starved for thymine increased the rate of DNA synthesis to at least twice its normal value; this suggests that extra rounds of chromosome replication can be induced in P. mirabilis as previously observed in Escherichia coli.