Pichia
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''Pichia'' (''Hansenula'' and '' Hyphopichia'' are obsolete synonyms) is a genus of
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...
s in the family Pichiaceae with spherical, elliptical, or oblong acuminate cells. ''Pichia'' is a teleomorph, and forms hat-shaped, hemispherical, or round
ascospore In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse Division (botany), division of fungi. After two parental cell nucleus, nuclei fuse, the ascu ...
s during sexual reproduction. The anamorphs of some ''Pichia'' species are '' Candida'' species. The asexual reproduction is by multilateral budding. The genus name of ''Pichia'' is in honour of Pico Pichi (1862–1933), who was an Italian
botanist Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...
and Professor of natural history and
plant pathology Plant pathology or phytopathology is the scientific study of plant diseases caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Plant pathology involves the study of pathogen identification, disease ...
at a viticulture school in the town of
Conegliano Conegliano (; Venetian language, Venetian: ''Conejan'') is a town and ''comune'' of the Veneto region, Italy, in the province of Treviso, about north by rail from the town of Treviso. The population of the city is of people. The remains of a 10th ...
in the
Province of Treviso The province of Treviso () is a Provinces of Italy, province in the Veneto region of Italy. Its capital is the city of Treviso. The province is surrounded by Province of Belluno, Belluno in the north, Province of Vicenza, Vicenza in the west, Pro ...
. The genus was circumscribed by Emil Christian Hansen in Centralbl. Bakteriol., 2. Abt., 12 on pages 533–538 in 1904.
Lactose Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from (Genitive case, gen. ), the Latin word for milk, plus the suffix ''-o ...
is neither fermented nor assimilated by these species. The behaviour with regard to other carbohydrates is dependent on the different species. Nitrate is always assimilated. More than 100 species of this genus are known.
GBIF The Global Biodiversity Information Facility (GBIF) is an international organisation that focuses on making scientific data on biodiversity available via the Internet using web services. The data are provided by many institutions from around the ...
lists 155. A number of ''Pichia'' species have been reassigned to other genera, see below. As a result,
Species Fungorum ''Index Fungorum'' is an international project to index all formal names (Binomial nomenclature, scientific names) in the fungus Kingdom (biology), kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partn ...
accepts only 32 species (see below for list).


Taxonomy

A number of species have been moved to other genera. These include moves to '' Wickerhamomyces'' (''W. canadensis'', ''W. ciferri'', ''W. lynferdii'', ''W. salvicola'' and ''W. subpelliculosa''), to '' Starmera'', to '' Cyberlindnera'', to '' Ogataea'' and many others.


Occurrence

Some ''Pichia'' (in the broad, pre-split sense) interfere with the fermentation process for alcohol production. In
winemaking Winemaking, wine-making, or vinification is the production of wine, starting with the selection of the fruit, its Ethanol fermentation, fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over ...
, some species of ''Pichia'' can create potential faults in wines. Most are found in decaying plants; some live in close
symbiosis Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biological interaction, between two organisms of different species. The two organisms, termed symbionts, can fo ...
with insects, which live on decaying plants. Some ''Pichia'' (sensu lato) representatives can be found in raw milk and cheese, such as '' P. anomala'' (now named ''Wickerhamomyces anomalus''). ''W. anomalus'' has been shown to combat the undesirable mold ''
Aspergillus flavus ''Aspergillus flavus'' is a saprotrophic and pathogenic fungus with a cosmopolitan distribution. It is best known for its colonization of cereal grains, legumes, and tree nuts. Postharvest rot typically develops during harvest, storage, and/or ...
'', which contaminates food sources such as tree nuts and corn, and produces aflatoxins. Researchers of the
Agricultural Research Service The Agricultural Research Service (ARS) is the principal in-house research agency of the United States Department of Agriculture (USDA). ARS is one of four agencies in USDA's Research, Education and Economics mission area. ARS is charged with ext ...
found that when pistachio trees were treated with ''W. anomalus'', the growth of ''A. flavus'' was inhibited up to 97%. In addition to inhibiting ''A. flavus'', the yeast may also help protect other agricultural crops from unwanted molds that affect the crop's taste, texture, yield, and safety. In smeared-surface ripened cheese, the most important species is '' P. membranifaciens'' that also occurs on cream cheese. The formation of a so-called pellicle is typical. Another former member of the genus, '' P. pastoris'' (now ''Komagataella phaffii''), is widely used in molecular biology and biotechnology as an expression system. '' P. angusta'' (now called ''Ogataea polymorpha''), is a model organism for studying the functions of
peroxisome A peroxisome () is a membrane-bound organelle, a type of microbody, found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen perox ...
s and their underlying molecular biology. Some ''Pichia'' species (e.g. '' P. ohmeri'', now ''Kodamaea ohmeri'') have recently been clinically proven to be pathogens, better known as so-called opportunistic pathogensPichia Species
, Doctor Fungus, url accessed 27 February 2014
in
immunocompromised Immunodeficiency, also known as immunocompromise, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that affe ...
humans.


Species

As accepted by
Species Fungorum ''Index Fungorum'' is an international project to index all formal names (Binomial nomenclature, scientific names) in the fungus Kingdom (biology), kingdom. As of 2015, the project is based at the Royal Botanic Gardens, Kew, one of three partn ...
; * '' Pichia barkeri'' * '' Pichia cactophila'' * '' Pichia cecembensis'' * '' Pichia cephalocereana'' * '' Pichia deserticola'' * '' Pichia eremophila'' * '' Pichia exigua'' * '' Pichia fermentans'' * '' Pichia galeiformis'' * '' Pichia garciniae'' * '' Pichia gijzeniarum'' * '' Pichia heedii'' * '' Pichia kluyveri'' * '' Pichia kudriavzevii'' * '' Pichia megalospora'' * '' Pichia membranifaciens'' * '' Pichia methanothermo'' * '' Pichia myanmarensis'' * '' Pichia nakasei'' * ''
Pichia nanzhaoensis ''Pichia'' (''Hansenula'' and ''Hyphopichia'' are obsolete synonyms) is a genus of yeasts in the family Pichiaceae with spherical, elliptical, or oblong acuminate cells. ''Pichia'' is a teleomorph, and forms hat-shaped, hemispherical, or round a ...
'' * '' Pichia nongkratonensis'' * '' Pichia norvegensis'' * '' Pichia occidentalis'' * '' Pichia paraexigua'' * '' Pichia porticicola'' * '' Pichia pseudocactophila'' * '' Pichia punctispora'' * '' Pichia rarassimilans'' * '' Pichia scaptomyzae'' * '' Pichia scutulata'' * '' Pichia sporocuriosa'' * '' Pichia terricola'' * '' Pichia uvarum''


References


External links


Pichia at Dr Fungus

Pichia in MycoBank.org
{{Authority control Saccharomycetaceae Yeasts Yeasts used in brewing