Osamu Namiki

Effect of inhibitors of nucleic acid and protein syntheses on the induced syntheses of bacteriochlorophyll and δ-aminolevulinic acid synthetase by Rhodopseudomonas spheroides

Abstract The dark-aerobically grown Rhodopseudomonas spheroides cells, which has no photosynthetic pigments, commenced to synthesize bacteriochlorophyll and carotenoids without detectable growth when the cells were transfered to dark semi-anaerobic incubation conditions. The level of δ-aminolevulinic acid synthetase increased over fourfold during the incubation. The induced synthesis of the pigments was almost completely inhibited by the addition of either acriflavin (2:8-diamino-10-methyl-acridine), chloramphenicol, mitomycin C or phleomycin to the incubation medium. The synthesis was also inhibited by actinomycin D and 8-azaguanine to considerable extents. The induced synthesis of δ-aminolevulinic acid synthetase, however, was scarcely affected by mitomycin C or phleomycin, whereas the synthesis was completely inhibited by chloramphenicol and acriflavin. The induced formation of catalase (H 2 O 2 : H 2 O 2 oxidoreductase, EC 1.11. 1.6) in light-anaerobically grown R. spheroides cells (brought about by incubating the cells under vigorous aeration) was not inhibited by mitomycin C but was inhibited by chloramphenicol and acriflavin. When mitomycin or acriflavin was added to the incubation mixture after the synthesis of pigments had commenced, the inhibition of the pigment synthesis became apparent only after an insusceptible period of about one hour, whereas the inhibition of δ-aminolevulinic acid synthetase began immediately after the addition of the inhibitors. The cells synthesizing photosynthetic pigments under dark semi-anaerobic conditions actively incorporated the radioactivity of [ 14 C]uracil into the DNA fraction as well as into the RNA fraction of the cells. The incorporation of radioactivity into both RNA and DNA was completely inhibited by acriflavin. Mitomycin inhibited the incorporation into DNA by 96%, whereas the inhibition by mitomycin of the incorporation into the RNA fraction was only 30%.