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J Bacteriol. 1973 April; 114(1): 152-163
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Competence for Deoxyribonucleic Acid Uptake and Deoxyribonuclease Action External to Cells in the Genetic Transformation of Diplococcus pneumoniae

¹ Biology Department, Brookhaven National Laboratory, Upton, New York 11973

ABSTRACT

A mutant of Diplococcus pneumoniae that apparently does not require activator can become competent for uptake of deoxyribonucleic acid (DNA) when grown in dilute cultures or in the presence of trypsin. Development of competence in both mutant and wild strains is temperature dependent, being 10-fold greater at 30 C than at 37 C. Induction of competence on a shift from 37 to 30 C requires protein synthesis and the presence of Mg²⁺ and Ca²⁺; uptake of DNA does not require protein synthesis. Competence decays exponentially at higher temperatures. As well as taking up DNA, competent cells release oligonucleotide fragments of donor DNA in the medium external to the cells. Normal strains release fragments comparable in amount to the DNA taken up; but, in a mutant selected for inability to degrade DNA in agar, the amount of fragments formed external to the cells is only 40% of DNA uptake. Requirements for external deoxyribonuclease action are identical to those for DNA uptake: prior development of competence and the presence during treatment with DNA of Mg²⁺ ions and a source of energy.

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