Pichia
Encyclopedia
Pichia is a genus of yeasts
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 in the family Saccharomycetaceae
Saccharomycetaceae
The Saccharomycetaceae are a family of yeast in the order Saccharomycetales that reproduce by budding. Species in the family have a cosmopolitan distribution distribution, and are present in a wide variety of habitats, especially those with a plentiful supply of carbohydrate sources...

 with spherical, elliptical or oblong acuminate cells. Pichia is a teleomorph, and forms during sexual reproduction hat-shaped, hemispherical or round ascospore
Ascospore
An ascospore is a spore contained in an ascus or that was produced inside an ascus. This kind of spore is specific to fungi classified as ascomycetes ....

s. The anamorphs of some Pichia species are Candida
Candida (genus)
Candida is a genus of yeasts. Many species are harmless commensals or endosymbionts of animal hosts including humans, but other species, or harmless species in the wrong location, can cause disease. Candida albicans can cause infections in humans and other animals, especially in immunocompromised...

species. The asexual reproduction is by multilateral budding.

Lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

 is neither fermented by this species nor assimilated. The behavior with regard to other carbohydrates is dependent on the different species. Nitrate is always assimilated.

Today more than 100 species of this genus are known. Some of them interfere with the fermentation process for alcohol production. Most are found in decaying plants, some live in close symbiosis
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 with insects, which live on decaying plants.

Some Pichia representatives can be found in raw milk and cheese, such as P. anomola (formerly named Hansenula anomala). P. anomala has been shown to combat the undesirable mold Aspergillus flavus
Aspergillus flavus
Aspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...

, which contaminates food sources such as tree nuts and corn, and produces aflatoxins. Researchers of the Agricultural Research Service
Agricultural Research Service
The Agricultural Research Service is the principal in-house research agency of the United States Department of Agriculture . ARS is one of four agencies in USDA's Research, Education and Economics mission area...

 found that when pistachio trees were treated with P. anomala 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. http://www.ars.usda.gov/is/pr/2010/100127.htm In smeared surface ripened cheese the most important species is P. membranifaciens
Pichia membranifaciens
Pichia membranifaciens is a plant pathogen.- External links :* *...

that also occurs on cream cheese. The formation of a so-called pellicle is typical. Another member of the genus, P. pastoris
Pichia pastoris
Pichia pastoris is a species of methylotrophic yeast. Pichia is widely used for protein expression using recombinant DNA techniques. Hence it is used in biochemical and genetic research in academia and the biotechnical industry....

is widely used in molecular biology and biotechnology as an expression system. P. angusta
Hansenula polymorpha
Ogataea polymorpha is a methylotrophic yeast with unusual characteristics. It is used as a protein factory for pharmaceuticals.Ogataea polymorpha belongs to a limited number of methylotrophic yeast species – yeasts that can grow on methanol...

furthermore called Hansenula polymorpha or H. polymorpha, is a model organism for studying the functions of peroxisomes
Peroxisome
Peroxisomes are organelles found in virtually all eukaryotic cells. They are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, polyamines, and biosynthesis of plasmalogens, etherphospholipids critical for the normal function of mammalian brains...

 and their underlying molecular biology.

Some Pichia species (eg P. ohmeri) have recently been clinically been proven to be pathogens, better known as so-called opportunistic pathogens
Opportunistic infection
An opportunistic infection is an infection caused by pathogens, particularly opportunistic pathogens—those that take advantage of certain situations—such as bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, one with a healthy immune system...

  in immunocompromised
Immunodeficiency
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

humans.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK