title: Incorporation of tritium into cell materials of Rhodopseudomonas spheroides from tritiated water in the medium under aerobic conditions.
abstract: When Rhodopseudomonas spheroides cells grown aerobically in the dark were incubated in medium containing tritiated water (THO), incorporation of T into the bacterial cell materials occurred under growth and no-growth conditions. The overall T incorporation under no-growth conditions was stimulated by vigorous aeration and was suppressed strongly in the presence of either 10(-3) M KCN or 0.3% HgCl2, indicating that the bulk of the incorporation might depend upon bacterial cell metabolism or respiration. 10 mug/ml chloramphenicol and 20 mug/ml rifamipicin slightly suppressed the T incorporation. The extent of T incorporation was proportional to the concentration of T in the medium. Accordingly, regardless of differences in the concentration of T in the medium, the maximum ratio of T content per hydrogen atom in the cell materials to that of THO in the medium was approximately 0.2 in non-growing cells and 0.5 in growing cells, whereas the value was 0.02-0.03 in cells incubated in medium containing KCN or HgCl2. The non-growing cells aerated in THO medium were lyophilized and fractionated by the modified method of Schneider. More than 40% of the total T incorporated into the cell materials was recovered in the cold PCA-soluble fraction, whereas the distribution of T into fractions solbule in ether-ethanol, hot PCA and alkali was 10 to 20% each. More than 75% of the T extracted in the cold PCA-soluble fraction was volatile. While the amounts of RNA and protein in the non-growing cells decreased on adding chloramphenicol or rifampicin, the distribution of T in these fractions did not change much. Our results on T incorporation into non-growing cells indicate that the major T incorporation into bacterial cell materials is independent of biosynthetic reactions using labeled precursors produced by the assimilation of T into metabolites, but presumably depends on energy-linked conformational changes of macromolecules.
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins / Q000378:metabolism; D002701:Chloramphenicol / Q000494:pharmacology; D003486:Cyanides / Q000494:pharmacology; D008628:Mercury / Q000494:pharmacology; D010101:Oxygen Consumption; D012242:Rhodobacter sphaeroides / Q000254:growth & development / Q000378:metabolism*; D012293:Rifampin / Q000494:pharmacology; D014316:Tritium; D014867:Water / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003486:Cyanides; D014867:Water; D014316:Tritium; D002701:Chloramphenicol; D008628:Mercury; D012293:Rifampin