''Alternaria tenuissima'' is a
saprophytic fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
and opportunistic plant pathogen. It is
cosmopolitan
Cosmopolitan may refer to:
Food and drink
* Cosmopolitan (cocktail), also known as a "Cosmo"
History
* Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953
Hotels and resorts
* Cosmopoli ...
in distribution, and can colonize a wide range of plant hosts.
Colonies of ''A. tenuissima'' produce chains on agar growth media.
The fungus often forms concentric ring patterns on infected plant leaves.
This species produces the allergen Alt a 1, one of the most important outdoor seasonal fungal allergens associated with allergy and asthma provocation.
In rare circumstances, this species is also known to infect immunosuppressed humans and animals.
Growth and morphology
Unlike many other species of ''Alternaria'', the conidiophores of ''A. tenuissima'' can develop in darkness after the colony has been exposed to light even very briefly; however its growth is more robust with longer periods of light exposure.
After 5–7 days in culture, colonies of ''A. tenuissima'' reach a diameter of 5 cm on
PCA or V-8
agar
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...
(vegetable juice agar).
Colonies grown on PCA are brown in colour with a loose, cottony texture and bearing golden-brown conidia in chains.
Conidia are on the areas of the colony that receive the most light exposure, forming concentric
sporulating
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
rings of uncrowded
conidial
A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to t ...
chains growing from branching
hypha
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
e on PCA.
Sporulation tends to be much more crowded in colonies grown on V-8 agar.
Simple unbranched and branched conidial chains of moderate length as well as solitary conidia are interspersed across the colony especially areas that receive little light.
The light, golden-brown colour of the conidia, and their tendency to taper into long beaks, distinguish ''A. tenuissima'' from similar species notably ''
A. alternata'' which produces dark brown conidia with short beaks.
Conidia of ''A. tenuissima'' also grow individually or in short chains
of 2-5 units,
while ''A. alternata'' tends to grow in longer chains.
''Alternaria tenuissima'' conidia are smooth-walled
and have a median and subconstricting transverse septum.
Colonies of ''A. tenuissima'' on natural substrates (e.g., plant leaves) often develop a concentric, ringed pattern.
Physiology
''Alternaria tenuissima'' is a
saprophyte, living on dead matter.
It produces the mycotoxins alternariol (AOH), alternariol methyl ester (AME), altenuene (ALT), altertoxin (ATX), and tenuazonic acid (TA), that are variously involved pathogenicity and interference competition.
Mycotoxins of this species are optimally produced at 25 °C.
Habitat and ecology
''Alternaria tenuissima'' is a
cosmopolitan
Cosmopolitan may refer to:
Food and drink
* Cosmopolitan (cocktail), also known as a "Cosmo"
History
* Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953
Hotels and resorts
* Cosmopoli ...
species, common on an array of various plant hosts in many countries spanning a range of environmental conditions.
It often colonizes blueberries,
tomatoes, grapevine, and strawberries.
It has also been found on several cereal grain species.
Optimal growth occurs between .
Although ''A. tenuissima'' is normally an opportunistic pathogen of plants, rare cases of skin infections in immunocompromised people have been reported.
Medical significance
Cutaneous and
subcutaneous alternariosis is a skin or tissue infection caused by members of the genus ''Alternaria'', most commonly ''A. alternata'' and ''A. tenuissima''.
Because of the inability of ''A. tenuissima'' to invade healthy host tissue, alternariosis tends to be restricted to people with abrogated cellular immunity and occasionally the elderly.
Complication following organ transplantion, Cushing's syndrome and immunosuppressive therapies are some of the typical settings in which alternariosis has been reported.
Alternariosis appears on the skin as red pustules that may produce ulcers over time.
''Alternaria tenuissima'' is a prolific producer of the
allergen
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.
In technical terms ...
Alt a 1.
Exposure to this protein can induce an allergic reaction in sensitized individuals by reacting with circulating
IgE
Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) " isotype") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε c ...
antibody
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
.
Exposure to Alt a 1 has been associated with asthmatic exacerbation.
''Alternaria tenuissima'' also produces the
mycotoxin tenuazonic acid which has received attention as a candidate antitumor medication.
References
External links
*
*
{{Taxonbar, from=Q4736374
tenuissima
Fungal plant pathogens and diseases