Cladosporium herbarum | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Dothideomycetes |
Order: | Capnodiales |
Family: | Davidiellaceae |
Genus: | Cladosporium |
Species: | C. herbarum
|
Binomial name | |
Cladosporium herbarum (Pers.) Link (1816)
| |
Synonyms | |
|
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]
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]
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]
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]
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]
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.
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]