Pichia
Pichia ( Hansenula synonym ) is a genus of true yeasts
Features
Microscopic characteristics
The cells are elongated with spherical, ovoid or short. Asexual reproduction occurs by multilateral shoot formation, which takes place from a narrow base. Pichia is a teleomorph, and forms asci are unconjugated or show a conjunction between mother cell and bud or between independent cells. Some species are heterothallic, but other homothallic. In the asci are 1-4, rarely 5-8 hat-shaped, hemispherical, saturn shaped or round ascospores formed which can be both smooth and rough.
Physiological / biochemical characteristics
No carbohydrates other than glucose are fermented. Only a few sugars and other carbon sources are assimilated. Nitrate is not used in contrast to other yeasts and related genera as the nitrogen source. Coenzyme Q7 is formed. The Diazoniumblau B reaction is negative.
Ecology
Many species are found in decaying plants such as Pichia membranaefaciens. The species can also occur in fermented beverages. Some Artem interfere with the fermentation process in alcohol production. Komagataella pastoris ( Pichia pastoris ) is frequently used in biotechnology as an expression system. Ogataea angusta ( Pichia angusta ), still known as Hansenula polymorpha or H. angusta, is a model organism to study the functions of peroxisomes and the molecular biology underlying their functions.
System
Emil Christian Hansen described the genus for the first time in 1904. Zur genus Pichia by association with Hansenula over 100 species have been recorded. The original separation was carried out as Hansenula species can assimilate nitrate. This feature of the genus separation, however, was later recognized as insufficient and Hansenula associated with Pichia. The genus was long at the Saccharomycetaceae within the Real yeasts. Meanwhile, they, together with three other genera ( Dekkera, Kregervanrija, Saturnispora ) own family who Pichiaceae. Since the genus itself, however, was polyphyletic genera Ogataea, Komagataella, Hyphopichia, Kodamaea, Kregervanrija, Nakazawaea, Pfaffomyces, Saturnispora, Lindneria, Starmera, Wickerhamomyces, Zygoascus and other genera were separated. This left about 20 species, with the type species Pichia membranifaciens:
- Pichia barkeri
- Pichia cactophila
- Pichia cecembensis
- Pichia cephalocereana
- Pichia deserticola
- Pichia eremophilia
- Pichia exigua
- Pichia fermentans
- Pichia heedii
- Pichia kluyveri
- Pichia kudriavzevii
- Pichia manshurica
- Pichia membranifaciens
- Pichia nakasei
- Pichia norvegensis
- Pichia orientalis
- Pichia pseudocactophila
- Pichia scutulata
- Pichia sporocuriosa
- Pichia terricola
Documents
- Yeast
- Ascomycota
- Ascomycota