Aureobasidium pullulans
Encyclopedia
Aureobasidium pullulans is a ubiquitous yeast
-like fungus that can be found in different environments (e.g. soil, water, air and limestone). It is well known as a naturally occurring epiphyte
or endophyte
of a wide range of plant species (e.g. apple
, grape
, cucumber, green beans, cabbage) without causing any symptoms of disease.
A. pullulans has a high importance in biotechnology
for the production of different enzymes, siderophores and pullulan
. Furthermore A. pullulans is used in biological control of plant diseases, especially storage diseases. In addition to the beneficial aspects, A. pullulans is in a few cases associated with plant disease (e.g. stigmatomycosis
on cotton
).
It can be cultivated on potato
dextrose agar
where it produces smooth, faint pink yeast-like colonies that are covered with a slimy mass of spores. Older colonies change to black due to chlamydospore
production. Primary conidia
are hyaline
, smooth, ellipsoidal, one-celled, and variable in shape and size; secondary conidia are smaller. Conidiophores
are undifferentiated, intercalary or terminal, or arising as short lateral branches. Endoconidia are produced in an intercalary cell and released into a neighboring empty cell. Hypha
e are hyaline, smooth, thinwalled, with transverse septa
. The fungus grows at 10–35 °C with optimum growth at 30 °C.
Chronic human exposure via humidifiers or air conditioners can lead to hypersensitivity pneumonitis
(aka extrinsic allergic alveolitis) or "humidifier lung
". This condition is characterized acutely by dyspnea
, cough, fever, chest infiltrates, and acute inflammatory reaction. Condition can also be chronic, and lymphocyte
mediated. Chronic condition is characterized radiographically by reticulonodular infiltrates in the lung, with apical sparing.
A. pullulans is notable for its phenotypic plasticity
. Colony morphology
may be affected by carbon source
, colony age, temperature, light and substrate
, with colonies ranging from homogeneous to sectored, yeast-like to filamentous growth, and from small to large. These changes, potentially influenced by epigenetic factors, and the particular developmental sequences that the colonies proceed through may be observed with the naked eye
.
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...
-like fungus that can be found in different environments (e.g. soil, water, air and limestone). It is well known as a naturally occurring epiphyte
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
or endophyte
Endophyte
An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life without causing apparent disease. Endophytes are ubiquitous and have been found in all the species of plants studied to date; however, most of these endophyte/plant relationships...
of a wide range of plant species (e.g. apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...
, grape
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...
, cucumber, green beans, cabbage) without causing any symptoms of disease.
A. pullulans has a high importance in biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
for the production of different enzymes, siderophores and pullulan
Pullulan
Pullulan is a polysaccharide polymer consisting of maltotriose units, also known as α-1,4- ;α-1,6-glucan'. Three glucose units in maltotriose are connected by an α-1,4 glycosidic bond, whereas consecutive maltotriose units are connected to each other by an α-1,6 glycosidic bond...
. Furthermore A. pullulans is used in biological control of plant diseases, especially storage diseases. In addition to the beneficial aspects, A. pullulans is in a few cases associated with plant disease (e.g. stigmatomycosis
Stigmatomycosis
The term Stigmatomycosis is the general name for a fungal disease that occurs in a number of crops, such as cotton, soybean, pecan, pomegranate, citrus, and pistachio. It has been reported on pistachio in Greece, Iran, Russia, and is frequently a problem in California pistachio orchards severely...
on cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
).
It can be cultivated on potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
dextrose agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
where it produces smooth, faint pink yeast-like colonies that are covered with a slimy mass of spores. Older colonies change to black due to chlamydospore
Chlamydospore
A Chlamydospore is the thick-walled big resting spore of several kinds of fungi. It is the life-stage which survives in unfavourable conditions, such as dry or hot seasons....
production. Primary conidia
Conidium
Conidia, sometimes termed conidiospores, are asexual, non-motile spores of a fungus and are named after the greek word for dust, konia. They are also called mitospores due to the way they are generated through the cellular process of mitosis...
are hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
, smooth, ellipsoidal, one-celled, and variable in shape and size; secondary conidia are smaller. Conidiophores
Conidium
Conidia, sometimes termed conidiospores, are asexual, non-motile spores of a fungus and are named after the greek word for dust, konia. They are also called mitospores due to the way they are generated through the cellular process of mitosis...
are undifferentiated, intercalary or terminal, or arising as short lateral branches. Endoconidia are produced in an intercalary cell and released into a neighboring empty cell. Hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e are hyaline, smooth, thinwalled, with transverse septa
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
. The fungus grows at 10–35 °C with optimum growth at 30 °C.
Chronic human exposure via humidifiers or air conditioners can lead to hypersensitivity pneumonitis
Pneumonitis
Pneumonitis or pulmonitis is a general term that refers to inflammation of lung tissue.Pneumonia is pneumonitis combined with consolidation and exudation...
(aka extrinsic allergic alveolitis) or "humidifier lung
Hypersensitivity pneumonitis
Hypersensitivity pneumonitis is an inflammation of the alveoli within the lung caused by hypersensitivity to inhaled organic dusts. Sufferers are commonly exposed to the dust by their occupation or hobbies.-Pathophysiology:Hypersensitivity pneumonitis involves inhalation of an antigen...
". This condition is characterized acutely by dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
, cough, fever, chest infiltrates, and acute inflammatory reaction. Condition can also be chronic, and lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
mediated. Chronic condition is characterized radiographically by reticulonodular infiltrates in the lung, with apical sparing.
A. pullulans is notable for its phenotypic plasticity
Phenotypic plasticity
Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship...
. Colony morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
may be affected by carbon source
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
, colony age, temperature, light and substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
, with colonies ranging from homogeneous to sectored, yeast-like to filamentous growth, and from small to large. These changes, potentially influenced by epigenetic factors, and the particular developmental sequences that the colonies proceed through may be observed with the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
.