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Killer toxin for sake yeast: properties and effects of adenosine 5'-diphosphate and calcium ion on killing action
Abstract:
The killer character of strain isolated from the main mash of sake brewing which produces a killer substance for sake yeast was transmitted to hybrids of the strain and a standard strain of Saccharomyces cerevisiae through a cytoplasmic determinant. The character was eliminated at 41 degrees C by incubation followed by growth at 30 degrees C. The killer strain produced the killer toxin in a growth-associated manner. A preparation of crude killer toxin extract showed first-order inactivation and a linear Arrhenius plot between 25 and 40 degrees C, with an activation of energy of 55.0 kcal/mol. Addition of 1% of synthetic polymer protected the toxin from inactivation by agitation but not by heat. Enhancement of the killer action toward sensitive yeast cells by only the nucleotide adenosine 5'-diphosphate (ADP) was observed after plating on agar medium as well as after incubation in liquid medium. The addition of CaCl2 reversed the enhancing effect of ADP on killing activity. This action of CaCl2 was inhibited by cycloheximide, suggesting that protein synthesis is required for recovery of toxin-induced cells in the presence of CaCl2. Further, CaCl2 overcame the decrease in the intracellular level of adenosine 5'-triphosphate (ATP) enhanced by ADP in killer-treated cells and also inhibited leakage of ATP from the cells with immediate response. The mode of killing action is discussed in terms of a transient state of the cells and the action of ADP and CaCl2.
Insights
A killer character in sake yeast, transmitted via cytoplasmic determinant, produces a toxin. This toxin
Area of Science:
- Microbiology
- Yeast Genetics
- Biochemistry
Background:
- Sake brewing involves yeast strains, some exhibiting 'killer' traits against sensitive yeast.
- Killer traits in yeast are often mediated by cytoplasmic factors and toxins.
- Understanding killer toxin mechanisms is crucial for fermentation control and yeast strain development.
Purpose of the Study:
- To characterize the killer trait in a sake yeast strain.
- To investigate the transmission and stability of the killer character.
- To elucidate the biochemical properties and mode of action of the killer toxin.
Main Methods:
- Hybridization of killer and standard Saccharomyces cerevisiae strains.
- Thermal inactivation studies of the killer toxin.
- Analysis of toxin activity enhancement by nucleotides and ions.
- Measurement of intracellular adenosine triphosphate (ATP) levels.
Main Results:
- The killer character is cytoplasmically inherited and can be eliminated by heat treatment.
- Killer toxin production is growth-associated and exhibits specific thermal inactivation kinetics.
- Adenosine 5'-diphosphate (ADP) enhances killer activity, while calcium chloride (CaCl2) reverses this effect.
- CaCl2 influences intracellular ATP levels and protects against toxin-induced ATP leakage, suggesting a role for protein synthesis in recovery.
Conclusions:
- The killer trait in this sake yeast is cytoplasmically determined and sensitive to specific environmental conditions.
- The killer toxin's activity is modulated by nucleotides and divalent cations.
- CaCl2 plays a significant role in mitigating toxin effects, potentially through ATP homeostasis and protein synthesis-dependent recovery mechanisms.