Truffles, baker's yeast and penicillin all come from the sac fungi
The biggest group of fungi, with more than 64,000 species, gives us bread, beer, cheese and antibiotics. It also contains rice blast, ergot and Candida, plus Cordyceps, a genus that parasitises and kills insects. What unites them is a microscopic sac that shoots out spores.
Ascomycota is a phylum of the fungal kingdom and, alongside the Basidiomycota, makes up the subkingdom Dikarya. Its hallmark is the ascus, named from the Greek for a wineskin: a tiny sexual structure inside which non-swimming spores called ascospores form. Members are nicknamed spore shooters for the way these elongated sacs launch their cargo. Familiar faces include morels, truffles, cup fungi and dead man's fingers, as well as the yeasts used by brewers and bakers.
Not every member bothers with sex. Some species never make asci at all, and in fact asexual reproduction is the main way the group spreads, allowing rapid colonisation of new ground. The usual method is producing conidia, spores named after the Greek word for dust, which arise by ordinary cell division and so are genetically identical to the parent. Yeasts reproduce instead by budding, a process in which the cell wall balloons outward. Asexual species were once lumped with the Basidiomycota; today DNA analysis and physical resemblance place them properly, and the phylum is recognised as a single lineage descended from one ancestor.
Humans lean on these fungi heavily. Fermentation of bread, alcoholic drinks and cheese depends on them, and Penicillium species both ripen cheeses and supply antibiotics against bacterial infections. Some insect-killing species, such as Beauveria, have worked well as biological pest control. In laboratories, Neurospora crassa, several yeasts and Aspergillus serve as standard model organisms for genetics and cell biology.
The darker side is disease. Candida albicans and Aspergillus niger can infect people, and several tens of species cause skin infections. Crops suffer from apple scab, rice blast, black knot, powdery mildews and the ergot fungi. The same phylum that leavens a loaf can wipe out a harvest.
Source: Ascomycota
