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C Stumm

Publications and source records attributed to C Stumm.

12 recordsLinked to original sources
PubMed1980

Physiological conditions affecting the sensitivity of Saccharomyces cerevisiae to a Pichia kluyveri killer toxin and energy requirement for toxin action.

The interaction between the killer toxin of Pichia kluyveri 1002 and cells of Saccharomyces cerevisiae SCF 1717 is strongly affected by the physiological state of sensitive cells. The killing effect is maximal for cells in the lag and early exponential phase of growth, whereas stationary cells are completely resistant. Furthermore, sensitivity is markedly enhanced by a rise of the pH (from 3.2 to 6.8) at which cells are cultured. Three successive stages can be distinguished in the killing process: (I) binding of the toxin to the primary binding site; (II) transmission of the toxin to its reactive site in the plasma membrane; (III) occurrence of functional damage (K+-leakage; decrease of intracellular pH). The transition from stage I to II is prevented in the absence of metabolic energy or at low temperature (below 10 degrees C). Sensitive cells in stage I can be rescued from toxin-induced killing by a short incubation at pH 7.0, which treatment is not effective for cells in stage II. Cells in stage II are able to resume growth when plated in a rich medium containing suitable concentrations of potassium and hydrogen ions. Rescue was not observed for cells in stage III of the killing process.

2,4-Dinitrophenol↗
PubMed1980

Effects of Pichia kluyveri killer toxin on sensitive cells.

The killer toxin produced by Pichia kluyveri 1002 kills yeast strains of the genera Candida, Saccharomyces and Torulopsis, including several S. cerevisiae killer strains. Binding of a lethal amount of the toxin to cells of S. cerevisiae SCF 1717 occurs rapidly after toxin addition. After treatment with the toxin for 10 min sensitive cells partially recovered when incubated under conditions that favor protein synthesis. Only after a lag time of 50--90 min sensitive cells changed physiologically. Killing of sensitive cells was characterized by leakage of potassium and adenosine 5'-triphosphate, decrease of intracellular pH, and inhibition of the active uptake of amino acids. These effects coincided with cell shrinkage and varied with incubation conditions. Uptake of the amino acid leucine in sensitive cells involved two apparently distinct transport systems (Km1 = 0.04 mM; Km2 = 0.46 mM). The toxin showed different effects on these transport systems.

Adenosine Triphosphate↗
PubMed1980

High incidence of sensitivity to yeast killer toxins among Candida and Torulopsis isolates of human origin.

Among yeast strains of human origin belonging to the genera Candida, Cryptococcus, Torulopsis, and Rhodotorula which were examined for killer and sensitive characteristics with killer and sensitive strains of Cryptococcus, Hansenula, Kluyveromyces, Pichia, Saccharomyces, and Torulopsis as screening organisms, a high incidence of sensitivity to killer toxins was observed within the genera Candida and Torulopsis. Of 142 strains tested, 116 strains distributed over all Candida and Torulopsis species examined were sensitive to one or more killers. Several new intergeneric killer-sensitive relationships are described. Furthermore, killing activity was exhibited by six strains of Candida (C. krusei, C. guilliermondii) and three strains of Torulopsis (T. glabrata).

Candida↗
PubMed1979

Production, purification and properties of a Pichia kluyveri killer toxin.

Production of the killer toxin of Pichia kluyveri 1002 was stimulated in the presence of yeast extract. In a minimal medium production was optimal at pH 3.8-4.0 and 22--25 degrees C. Addition of gelatin and nonionic detergents, like Brij-58 (polyoxyethylene 20 cetyl ether) and Triton-X-100, to this medium enhanced production significantly. The killer toxin was purified 140-fold by use of a stepwise ethanol precipitation and butyl Sepharose column chromatography. The purified killer toxin, which still contained some carbohydrates, appeared to be glycoprotein with a mol wt of about 19 000 and an isoelectric point of 4.3. It was stable between pH 2.5 and 4.7 and up to 40 degrees C.

Ascomycota↗
PubMed1977

The effect of amino acids on the motile behavior of Bacillus subtilis.

Constant levels of amino acids enhanced the velocity of Bacillus subtilis 60015 cells about 2-fold and stimulated the response in motility assays. The stimulation of velocity did not occur via the receptors for chemotaxis. Cysteine and methionine, general inhibitors of chemotaxis, both completely inhibited the smooth response in a temporal gradient of attractant. After methionine starvation B. subtilis 60015 showed no measurable response in a temporal gradient of attractant, this in contrast to the effect observed with some other bacteria. Addition of methionine to starved cells restored the response toward attractant. Revertants of B. subtilis 60015 for methionine requirement could not be starved and showed a normal behavior toward temporal gradients of attractant.

Adenosine Triphosphate↗
PubMed1977

Killer-sensitive relationships in yeasts from natural habitats.

Yeast strains (157) belonging to at least 9 genera were isolated from natural habitats and screened for killer-sensitive relationships. Killer and sensitive characteristics were exhibited by 17 and 11% of the isolates, respectively. The strains belong to either one of two mutually exclusive killer-sensitive groups.

Antibiosis↗
PubMed1977

Removal of Escherichia coli in wastewater by activated sludge.

Removal of bacteria from wastewater treated with activated sludge was studied by the use of a streptomycin-resistant Escherichia coli strain. The removal appeared to be a biphasic process. A rapid sorption of bacteria to the sludge flocs took place in the first hour after seeding mixed liquor with E. coli. Thereafter, slower elimination of E. coli was observed. The latter process was due to predation on E. coli by ciliated protozoa. This was shown by: (i) appearance of fluorescent food vacuoles of ciliates when fluorescent E. coli cells were added to mixed liquor; (ii) inhibition of predation either in the presence of cycloheximide or under anaerobic conditions; and (iii) absence of predation in bulking and washed sludge.

Anaerobiosis↗
PubMed1976

Chemotaxis and transport of amino acids in Allomyces arbuscula.

Among a number of amino acids tested, L-lysine and L-arginine are the principal attractants in the chemotaxis of the zygotes of Allomyces arbuscula. The reaction can be stimulated to a greater or lesser extent by a number of compounds chemically related to L-leucine. No relationship between transport of attracting amino acids and their effect on chemotaxis has been found.

Amino Acids↗
PubMed1975

Polyribosomes in different stages of the life cycle of the water mold Allomyces arbuscula.

Synchronous gametogenesis in the water mold Allomyces arbuscula is blocked by actinomycin D added at the onset of the process. Formation of the male gametangium can be selectively inhibited by administering actinomycin one hr after the induction of gametogenesis. The polyribosome pattern obtained after density gradient centrifugation remains virtually unchanged throughout gametogenesis until a stage immediately preceding maturation of the gametes. When ribosome from gametes and swarming zygotes are analyzed on gradients, some RNase-sensitive materials is found to band in the heavier portion of the gradient. Its presence suggests that some messenger RNA associated with ribosomes is conserved in the swarming cells. During gametogenesis RNA is de novo synthesized and becomes associated with the polyribosomes.

Cell Fractionation↗