Cladosporium herbarum (Pers.) Link 1816

Cladosporium herbarum is a common fungus found worldwide in organic and inorganic matter.^[1][2] It is efficiently distributed in the air, where it exists as the most frequently occurring fungal species.^[1][2][3] It can grow over a wide range of temperatures including very cold environments, giving it the ability to grow on refrigerated meat and form "black spots".^[1][3][4] Its high prevalence in the air and production of allergens makes C. herbarum an important exacerbant of asthma and hay fever.^[5][6]

Prevalence

Cladosporium herbarum is the type species of the genus Cladosporium.^[5][7] Its spores are highly prevalent in the air; the genus Cladosporium is the dominant genus of spores found in the air, with the C. herbarum species contributing the highest percentage to this group.^[2] These airborne spores are more common during the summer and fall seasons;^[2] in the summer there can be as many as 15,000 spores per m³ air of C. herbarum.^[8] Cladosporium herbarum is also found all over the world on dead organic material, in the soil, and sometimes appears as a plant parasite.^[9][2] It is also a common fungus found in indoor environments.^[8][10]

Growth

In young cultures, newly-formed spores show growth by budding into a large, multi-branched mycelium.^[1] It has an optimal growth temperature between 18 °C (64 °F) and 28 °C (82 °F), with a maximum growth temperature between 28 °C (82 °F) and 32 °C (90 °F).^[2][11][10] It has been shown to grow at temperatures as low as −6 °C (21 °F),^[2][10] and −10 °C (14 °F);^[11] allowing it to grow actively (albeit slowly) on frozen materials.^[5] Cladosporium herbarum can also grow in dry environments (xerophile).^[5][12] C. herbarum grows optimally at pH 6 but tolerates environments with a pH as low as 4.4.^[2] Conidium production is higher in wet than dry conditions.^[2] The production of spores is inhibited by rubratoxin B and aflatoxin.^[2][13] Its growth is inhibited in atmospheres of reduced oxygen^[11] and increased carbon dioxide.^[2] Mycosphaerella tassiana is the sexual reproductive stage (teleomorph) of C. herbarum.^[5][2]

Morphology

Spores produced by C. herbarum can be lemon-shaped or cone-shaped, often composed of 2-4 cells (3-23 mm).^[5][14][15] One-celled conidia (5.5-13 x 3.8-6 µm) also exist.^[2][11] In culture, newly-formed spores appear mostly 1-celled, later forming tree-like colonies with multiple branches.^[1] The stalks which produce C. herbarum spores are 250 µm long and 3-6 µm wide.^[2][15] They appear swollen at the tip and in between cells, and have irregularly bent branches.^{[2][15][11][10]} Under microscopy, these stalks appear pale or dark brown in color and have smooth or rough walls.^[15][11][10] When submerged in fluid, they become brittle and break up completely into spores and rod-like fragments.^[1] Colonies grown on Czapek yeast extract agar (CYA) and malt extract agar (MEA) appear velvety or fluffy, with smooth or slightly wrinkled walls, and are green or brown in color.^[15][2] The reverse side of the colony appears a darker green or grey/black.^{[15][2][10][1]} Colonies can appear both sparse or densely grown.^[11] At 5 °C (41 °F), colonies are 1-2 mm in diameter.^[11]

Habitat and ecology

This species is distributed worldwide, inhabiting polar, temperate, mediterranean, subtropical, tropical, forest, grassland, and arable soil regions.^[2] It is found frequently in wood exposed to soil, deep soil depths, and the highly nutritious soil directly surrounding the roots of plants (rhizosphere).^[2] It is one of the early colonizers on dying and dead plants (saprobe), especially the leaves and stems of both aquatic and desert plant species (for example ferns and mosses).^[2][15] It is the most common fungal species found on living leaves (given suitable conditions) and dead plant material in very moist environments.^[2][4] It also has an adaptation to high salt concentrations^[2] (has been found in high salinity sediments) and extremely dry areas (xerophilic).^[2]

Cladosporium herbarum causes spoilage of fresh fruits and vegetables including yams, peaches, nectarines, apricots, plums, cherries, tomatoes, and melons.^[11] Its common occurrence on fresh apples can lead to contamination of apple juice and fruit based products.^[11] It has also been found in eggs, hazelnuts, cereals, chickpeas, soybeans, and frozen fruit pastries.^[11] Cladosporium herbarum can also spoil cheese and pasteurized soft cheese, causing problems during its manufacturing.^[13] Being able to survive at temperatures below freezing, C. herbarum can cause “black spot” spoilage of meat in cold storage (between −6 °C (21 °F) and 0 °C (32 °F)).^[4][13] It has been isolated from fresh, frozen, and processed meats.^[11]

Cladosporium herbarum has been isolated from caterpillars, nests, feathers, pellets of free-living birds, nests of gerbils, bee honeycombs, internal organs of frogs, and earthworms.^[2] It has also been found indoors on walls, wallpaper, textiles, rubber strips of window-frames, and bathrooms.^[10] Increased release of C. herbarum spores is correlated with increasing temperatures, daylight, and declining humidity.^[2][4][10] This species appears more frequently during the summer than the winter with peak concentrations of airborne spores found during the afternoon of a 24 hour cycle.^[4][10] The spores are easily carried through the air and can be transported long distances including over oceans.^[2]

Pathogenicity

This fungus is non-pathogenic, but its ability to freely produce spores that are easily dispersed in air currents adds to its effect as a fungal airway allergen; it is one of the main fungal causes of asthma and hay fever in the Western Hemisphere.^[5][6] More than 60 antigens derived from C. herbarum have been detected, and 36 of these have immunoglobulin E (IgE) binding properties.^[16][5] Most of these antigens are proteins found inside cells,^[6][5] and eight of these antigens are members of the World Health Organization's official allergen list.^[5] There is variation in allergen content between different strains of C. herbarum .^[10]

Toxic effects of C. herbarum on warm-blood animals have been reported when they were fed with heavily infected wheat.^[2] It can produce a toxin causing mucosal damage in horses, and mycelium extracts are shown to have low-level toxicity in chicken embryos.^[5]

C. herbarum is also fungal plant pathogen. Its hosts include Bryum, Buxbaumia, Gyroweissia, Tortula, and Dicranella.^[17] It can cause Cladosporium ear rot on corn.

Molecular genetics

Most often, C. herbarum conidia have 1 nucleus, but some can have 2 nuclei.^[2] During mitosis, 5 to 8 dot-like chromosomes have been observed.^[2] Based on DNA analysis, they have a guanine-cytosine content (GC-content) of 55%.^[2] Using molecular diagnostics, C. herbarum internal transcribed spacer (ITS) sequences have been found to be identical to those of Cyphellophora laciniata.^[15]

References

Cladosporium herbarum è un fungo microscopico. È la specie di Cladosporium più comune e rappresenta uno dei primissimi colonizzatori dei substrati organici, delle piante morte o in fase morente, risultando molto frequente nel legno in decomposizione e sul legno esposto al suolo.^[1]

Aspetto

Le colonie raggiungono un diametro di 3-3.7 cm in dieci giorni su mezzo di coltura MEA (Malt Extract Agar) a 20 °C. Presentano un colore dal verde-olivaceo all'olivaceo-marrone o all'olivaceo-nero. Non sopravvive al trattamento con calore a 50-60 °C per 30 minuti.

Note

Cladosporium herbarum (Pers.) Link – gatunek grzybów z klasy Dothideomycetes^[1]. Bardzo pospolity grzyb mikroskopijny, saprotrof lub słaby pasożyt rozwijający się głównie na powierzchni martwych lub żywych części roślin. W laboratoriach często powoduje zanieczyszczenie kultur. U zbóż wywołuje czerń zbóż, dla ludzi jest jednym z ważniejszych alergenów^[2]. Powoduje zapalenie rogówki i alergiczną grzybicę płuc^[3].

Systematyka i nazewnictwo

Pozycja w klasyfikacji według Index Fungorum: Cladosporium, Cladosporiaceae, Capnodiales, Dothideomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi^[1].

Po raz pierwszy zdiagnozował go w 1794 r. Christiaan Hendrik Persoon nadając mu nazwę Dematium herbarum. Obecną, uznaną przez Index Fungorum nazwę nadał mu Johann Heinrich Friedrich Link w 1816 r.^[1]

Ma około 50 synonimów. Według Index Fungorum są nimi również wszystkie, liczne formy i odmiany^[4].

Morfologia i rozwój

Anamorfa na podłożu MEA rozwija się dobrze. Tworzy aksamitne kolonie o barwie od oliwkowozielonej do oliwkowobrązowej. W momencie tworzenia zarodników stają się czarne. Konidiofory o gładkich ścianach, długości do 250 μm i szerokości 3-6 μm. Wyrastają z napęczniałych strzępek. Konidia o kształcie od elipsoidalnego do cylindrycznego, z zaokrąglonymi końcami, wyraźnie brodawkowane, z wypukłymi, brązowymi bliznami. Są jedno, dwu, lub wielokomórkowe. Konidia jednokomórkowe mają wymiary 5,5-13,0 × 3,8-6,0 μm^[3].

Przypisy

Cladosporium herbarum je grzib^[5], co go nojprzōd ôpisoł Christiaan Hendrik Persoon, a terŏźnõ nazwã doł mu Heinrich Friedrich Link 1816. Cladosporium herbarum nŏleży do zorty Cladosporium i familije Davidiellaceae.^[6][7] Żŏdne podgatōnki niy sōm wymianowane we Catalogue of Life.^[6]

Przipisy

• 1 Описание
• 2 Экология и значение
• 3 Таксономия
  • 3.1 Синонимы
• 4 Примечания
• 5 Литература