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Predacious yeasts
1Department of Plant Sciences, University of Western Ontario, London, Canada.
Abstract:
Haustorium-mediated predation was observed in seven yeast species. Arthroascus javanensis, Botryoascus synnaedendrus, Guilliermondella selenospora, Saccharomycopsis fibuligera, and three hitherto unknown species penetrate and kill other yeasts. These yeasts share an unusual requirement for organic sulphur. One isolate recovered from Australian Hibiscus was studied in detail and found to attack a broad range of prey species, including ascomycetous and basidiomycetous yeasts as well as moulds. Predation was most effective when growth was on a solid surface and the medium was poor in complex nutrients. Organic sulphur (exemplified by methionine) was identified as a key factor. It serves as a nutritional benefit to the predator and, depending on the concentration, acts as either an inhibitor of predation or possibly a signal for detection of prey. Sampling of a yeast habitat with a medium selective for selenium-resistant yeasts indicated that auxotrophic and predacious yeasts might be more widespread than anticipated.
Insights
Seven yeast species exhibit haustorium-mediated predation, requiring organic sulfur for this predatory behavior. This finding suggests predacious yeasts may be more common than previously thought.
Area of Science:
- Mycology
- Yeast Biology
- Predatory Microorganisms
Background:
- Haustorium-mediated predation is a rare but significant interaction in microbial ecosystems.
- Several yeast species have been identified as predators, but the underlying mechanisms and requirements are not fully understood.
Purpose of the Study:
- To identify and characterize yeast species capable of haustorium-mediated predation.
- To investigate the nutritional requirements and environmental factors influencing this predatory behavior.
Main Methods:
- Isolation and identification of seven predatory yeast species, including novel ones.
- Detailed study of one isolate's prey range and predation efficiency under varying conditions.
- Analysis of the role of organic sulfur, specifically methionine, in predation.
Main Results:
- Seven yeast species, including Arthroascus javanensis and Saccharomycopsis fibuligera, were confirmed to prey on other yeasts via haustoria.
- Predation effectiveness is enhanced on solid surfaces with nutrient-poor media.
- Organic sulfur (methionine) is crucial, acting as a nutrient and a potential signaling molecule, with concentration-dependent effects on predation.
Conclusions:
- The study expands the known diversity of predatory yeasts and highlights their unique requirement for organic sulfur.
- Environmental conditions significantly influence the efficacy of yeast predation.
- Predacious yeasts may be more prevalent in natural habitats than previously recognized, particularly in specialized niches.