Effects of radiophosphorus decay on some synthetic capacities of bacteria

Abstract

1. 1. Aliquots of a 32P-labeled culture of Escherichia coli which have been starved for phosphorus to various degrees and which contain various total and relative amounts of ribonucleic (RNA) and deoxyribonucleic (DNA) acid lose their viability with radioactive decay at the same final rate. This supports a previous conclusion that the disintegrations of 32P atoms in the bacterial DNA are principally responsible for the decay-induced loss of viability of bacterial cells. 2. 2. The capacity of 32P-labeled cultures of E. coli to form two induced enzymes (β-galactosidase and d-serine deaminase) and two constitutive enzymes (β-galactosidase and l-threonine deaminase) is lost with radioactive decay at the same rate as viability. Radioactive decay, furthermore, destroys the capacity to form the two induced enzymes more rapidly in bacteria which are uniformly 32P-labeled in all their phosphorylated constituents than in bacteria which are preferentially labeled in their RNA. 32P-labeled bacterial populations in which the normal ratio of the amounts per cell of RNA to DNA has been reduced by phosphorus starvation, lose their enzyme-forming capacity at the same rate as non-starved, RNA-rich cells. These observations suggest that, as for loss of viability, decay of 32P atoms in the bacterial DNA is principally responsible for loss of enzyme-forming capacity. 3. 3. The capacity of 32P-labeled E. coli cultures for synthesis of RNA and protein is also destroyed by radioactive decay, albeit at a rate which is somewhat less than the rate of loss of viability or capacity for enzyme formation of the same bacteria. 4. 4. From these experiments it is concluded that the DNA of the bacterial cell functions as an integral unit in the synthesis of its enzymes.