Rapidly labeled ribonucleic acids of Rhodopseudomonas spheroides under varying conditions of catalase synthesis

Abstract

The relationship between the apparent composition of rapidly labeled RNA and the synthesis of a protein — in the present instance, of catalase (H 2O 2:H 2O 2 oxidoreductase, EC 1.11.1.6) — was studied in a wild strain (2.4.1) and a constitutive high-catalase mutant (CCl) of Rhodopseudomonas spheroides. The nucleotide composition of the total RNA of these two strains was determined under several conditions of growth as well as that of ribosomal and soluble RNA and DNA. Pulses of inorganic [ 32P]phosphate, and in many instances also of [ 14C]uracil, were applied to the cultures under a variety of physiological conditions and, in the case of the wild strain, without and with the induction of catalase formation. The nucleotide composition of the rapidly labeled RNA remained, with one exception, unchanged in all experiments, regardless of far-reaching metabolic shifts that must have taken place; it did not resemble that of DNA, but was intermediate between a DNA-like RNA and ribosomal RNA. Only the rapidly labeled RNA of the high-catalase mutant in the stationary stage showed a divergent composition which was, however, even farther removed from that of DNA. The induction of catalase in the wild strain was without effect on the incorparation of uracil into RNA, nor was the uptake of the precursor by the RNA of different cellular fractions influenced by enzyme induction. It must be concluded that, if a shift towards the massive production of catalase is accompanied by the appearance of a species of RNA having a characteristic composition, this has not been demonstrated in the studies presented here.