Hiivasienet

Hiivasienet are a broad group of unicellular fungi characterized by their ability to grow as single cells, typically oval or elongated, and to reproduce primarily by budding. As a morphological grouping rather than a single lineage, yeasts occur in several fungal phyla, most notably the Ascomycota and the Basidiomycota.

Biology and life cycle: Yeasts are usually facultative anaerobes that ferment sugars to ethanol and carbon dioxide, a metabolism widely used in baking and brewing. They can also respire aerobically when oxygen is present. Many species exhibit a haploid-diploid life cycle and can switch to filamentous or pseudohyphal growth under nutrient limitation. The most studied yeast, Saccharomyces cerevisiae, serves as a model organism in genetics and cell biology.

Ecology and habitats: Yeasts are found on plant surfaces, in fruits, nectar, soil, and the guts of insects and other animals. They are common members of the microbiota on skin and mucous membranes in humans and animals. While most yeasts are harmless, some species are opportunistic pathogens, such as Candida albicans, which can cause infections in immunocompromised individuals.

Industrial and scientific relevance: Yeasts are essential in food and beverage production, enabling bread leavening, beer and wine fermentation, and industrial bioethanol production. They are also important in biotechnology and research, where yeast cells are used for recombinant protein production, functional genomics, and as model systems for fundamental cellular processes.

Safety and regulation: Yeasts used in food and industry are generally regarded as safe when handled according to standard hygiene and biosafety practices. Pathogenic yeasts are managed under clinical guidelines to prevent or treat infections.