Susumu Nagai

High-frequency production of respiratory mutants in yeast under nutritional deficiencies

Abstract Production of respiration-deficient mutants in unusually high frequencies up to 100% was observed when an originally stable, normal culture of yeast was grown in Schopfer s medium which is very simple and lacking in vitamines. The mutant production was significantly reversed, often to the minimal spontaneous level by addition of biotin, pantothenate, yeast extract and several amino acids, and also by substitution of the asparagine in Schoffer s medium with several nitrogenous nutrients. Such a production of respiratory mutants under nitritional deficiencies was found to be dependent largely upon the yeast species and strain. Two strains of Saccharomyces cerevisiae var. ellipsoideus readily produced 100% mutants. A few others produced close to 100% mutants after successive transfers, repeated 3 to 4 times, in Schopfer s medium. Yet other species remained normal even after repeated passages. Nutritional background conditions for hereditary maintenance of respiratory competence are discussed.

Counteracting effect of eosin and related dyestuffs on the production of respiration-deficient mutants in yeast by 4-nitroquinoline 1-oxide

Production of respiration-deficient (rho-) mutants under growing conditions in a strain of Saccharomyces chevalieri by 4-nitroquinoline 1-oxide (4NQO), a potent carcinogen, reached 100%. The mutation frequency was considerably reduced when eosin Y was applied in various combinations with 4NQO. The counteracting effect was slight when eosin Y was applied concurrently with 4NQO, but was very strong and persistent when eosin Y was impregnated into the yeast cells before their exposure to 4NQO. Eosin B, erythrosin B and uranin also showed more or less counteracting effects agains 4NQO in producing the rho- mutants. Possible mechanisms for the counteracting effects of these dyestuffs against 4NQO are discusses in relation to antimutagenesis and chemotherapeutic interference.

Stabilizing effect of caffeine on a respirationally unstable strain of yeast

Abstract A respirationally unstable strain R6U2 of haploid yeast spontaneously produced respiration-deficient (RD) mutants in unusually high frequencies. Addition of small doses up to 1200 mg/l of caffeine to the culture media considerably reduced the production of RD mutants. The effect was only temporary and the RD mutants again appeared in high frequencies when the cultures were freed from caffeine. It was demonstrated that caffeine rendered the strain more stable and reduced the production of mutant progeny from the normal but unstable mother cells.

Methylene blue and toluidine blue interfering with the production of respiration-deficient mutants in yeast by acriflavine

Abstract Methylene blue and toluidine blue, which are ineffective to produce respiration-deficient mutants of yeast, counteract the effect of acriflavine in producing the mutants. Magdala red and rhodamine B, which do not produce the mutants by themselves, do not counteract acriflavine.

Production of respiration-deficient mutants of yeast by some quinone-imine dyes.

Abstract Basic quinone-imine dyes were tested for their effect in producing respiration-deficient mutants of bakers yeast. Some dyes of a subclass, azine dyes (Table I) were found to be effective, but neutral red was ineffective. Janus green B, which is ordinarily classified as an azo dye, was also tested and found to be strongly effective. Oxazine and thiazine dyes so far tested (Table II) were ineffective except one. This exception was Nile blue, an oxazine dye, of which a preparation from Grubler was strongly effective, while those from Tokyo Kasei and Merck were only weakly effective. The dyes were examined by paper chromatography. Development with acetone-water (4:6) and tert. -butanol-acetic acid-water (4:1:5) gave fairly good results. A few dyes were satisfactorily pure, but many others separated into two or more components. Efficacy of the dyes to produce the respiration-deficient mutants in relation to the chemical properties was discussed.

Interferences between some inducers of the respiration-deficient mutation in yeast.

Abstract Various inducers of the respiration-deficient mutation in yeast interfere with each other when they are applied jointly to a strain of bakers yeast. The combinations tested comprise acriflavine, pararosanilin, pyronin B, pyronin Y, acridine red 3 B and caffeine. The interferences are apparent in the combinations of sub-optimal doses of one inducer with sub-threshold doses of another inducer. Either counteractive or promotive interferences depending on the combinations are observed. Promotive interferences also appear in some combinations of sub-threshold doses of two inducers. The inducers remain indifferent to each other in some combinations. Interpretations on the mechanism of the interferences are presented with reference to the mutagen-antimutagen relations and therapeutic interferences.

Spectrophotometry of yeast cells colored alive with acriflavine and other basic dyes

Abstract Yeast cultures were grown in nutrient media containing acriflavine and several other basic dyes. Colored cells thus produced were examined by spectrophotometry in comparison with the original dye solutions. Eight out of ten dyes tested showed, when bound firmly to yeast cells, their absorption maxima displaced to a wavelength region longer than that in the corresponding solutions. Mixtures of acriflavine with some other dyes produced accordingly mix-colored cells, in which two dyes appeared bound side by side. Relationships of the coloring to production of respiration-deficient mutants are discussed.

Brom Cresol Green and Brom Phenol Blue as Indicators of Respiration Deficiency in Yeast

Strains of Saccharomyces which contained cells of respirationally normal (wild-type) and of respiration-deficient (RD) mutants were grown on untrient agar plates containing 20–23 mg/liter of either brom cresol green (BCG) or brom phenol blue (BPB). Glucose content of the media was varied experimentally in the range of 1.5–6%. After 2-4 days of incubation, normal colonies were very palely stained whereas RD colonies were drak green with BCG and dark blue with BPB. Optimum glucose content in the medium was 2-3% for S. cerevisiae, S. carlbergensis and S. chevalieri, but Fleischmanns (bakers) yeast developed the best color contrast with 4–5% glucose.

Victoria blue and night blue affecting the production of respiration-deficient mutants in yeast☆

Abstract Victoria blue 4R, Victoria blue B and night blue are effective to induce the respiration-deficient mutation in bakers yeast. But the efficacy is rather low as compared with that of many other basic dyes. Those dyes under discussion are differentially toxic to the normal and repiration-deficient cultures, suppressing the latter at one-sixth to one-eighth times as low levels as those for the former. Very small doses of those dyes often interfere counter-actively with some other inducers, namely acriflavine, pararosanilin, pyronin B, pyronin Y and caffeine. But they sometimes act promotively when their doses are close to the threshold levels, respectively. A strikingly promotive interference appears when they are applied in combination with acridine red 3B. Some possible relationships of the molecular configurations in those dyes to the unusual effects are discussed.

Reduction of silver nitrate by cystoliths ofFicus elastica

SummaryThe cystoliths ofFicus elastica turn dark when a 2 per cent solution of silver nitrate is applied to the leaf sections. The cystoliths appear as if they reduce the silver ions and impregnate themselves with metallic silver. The reducing activity is, however, accounted for by ascorbic acid, and not by the cystoliths in themselves. The darkening reaction takes place in the presence of ascorbic acid either natively contained in fresh leaves or exogenously replenished after killing of the leaf sections. The cystoliths can react, however, only when they maintain the calcareous cortex intact. The reaction no longer occurs even in the presence of ascorbic acid when the cystoliths have been deprived of the cortex by exposure to Na2-EDTA.