Chaetomium atrobrunneum | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Sordariomycetes |
Order: | Sordariales |
Family: | Chaetomiaceae |
Genus: | Chaetomium |
Species: | C. atrobrunneum
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Binomial name | |
Chaetomium atrobrunneum Ames (1949)
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Synonyms | |
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Chaetomium atrobrunneum is a darkly pigmented mould affiliated with the fungal division, Ascomycota. [1] [2] [3] This species is predominantly saprotrophic, [2] although it has been known to infect animals including humans, showing a proclivity for the tissues of the central nervous system. [4] [5] Chaetomium atrobrunneum was described in 1949 from a mouldy military mattress cover obtained from the island of Guadalcanal. [6]
Chaetomium atrobrunneum is a darkly pigmented, predominantly mycelial fungus. [2] Colonies of C. atrobrunneum typically are dark grey to black in colour with a woolly appearance. [1] It forms sexual fruiting structures called perithecia that are spherical to oval in shape, [7] measuring between 70 and 150 μm in width when fully matured at 10 days. [1] The perithecia are covered sparsely with straight, finely-blistered, dark brown hairs that become occasionally become broadly branched with age. [1] [3] The perithecia contain asci within which are 8 ascospores that spindle-shaped, have a single sub-apical germ pore and are brown to grey in colour, [1] [3] although a mutant with colourless ascospores has been reported. [8] The ascospores of this species are smooth-walled and measure 9–11 μm in length by 4.5–6 μm in width. [1] [3]
Chaetomium atrobrunneum has been reported from rabbit dung, [7] milled Italian rice, [9] water-damaged building materials, concrete, plaster and wallpaper. [10] Chaetomium atrobrunneum grows more slowly at 25 °C (77 °F) than most other species of the genus, [1] [3] reaching a colony diameter of 16–21 mm after 7 days incubation on Cornmeal Agar (CMA). [11] By contrast, its growth at higher temperatures is much more rapid than many other Chaetomium species, producing colonies of approximately 41–44 mm in diameter after 7 days incubation at 42 °C (108 °F) on CMA. [3] [11] Chaetomium atrobrunneum is distinct from other Chaetomium species by its smaller perithecia, its ability to grow at relatively high temperatures, [3] and the occasional presence in this taxon of perithecial hairs that branch at wide angles. [6]
Chaetomium atrobrunneum is strongly cellulolytic, [12] and cellulose-containing growth media can be used to selectively cultivate this and other Chaetomium species. [13] This species has also been reported to produce chaetoatrosin A, a selective inhibitor of chitin synthase II. This enzyme is involved in septum formation and cellular division, [14] and its inhibition by chaetoatrosin A is thought to be the mechanism underlying the antifungal effects of C. atrobrunneum culture filtrates against several medically important fungi including Cryptococcus neoformans. [14]
Chaetomium atrobrunneum is a rare pathogen of humans that tends to infect the tissues of the central nervous system. [1] Its pathogenicity is thought to be supported by its ability to grow at high temperatures. [1] [2] This species has been reported to be an agent of fatal brain abscesses in immunologically impaired people. [1] [3] [11] It can also cause systemic disseminated phaeohyphomycosis [5] affecting other organs including the lungs. [11] Infections due to this species have typically occurred following invasive procedures such as intravenous drug administration and renal transplantation. [11]
In addition to deep mycotic disease, C. atrobrunneum is known to eye diseases including retinitis [15] and keratitis, [16] manifesting with symptoms of pain, redness and watering of the eye, and swelling of the eyelid and surrounding tissues. [16] Corneal infections have responded to dual therapy with topical natamycin and oral ketoconazole. [16] This species has been reported from infections of the skin surrounding the eye. [17] Co-administration of the antifungal drugs fluconazole (delivered topically) and itraconazole (delivered orally) have been effective in the treatment of cutaneous disease. [17] Skin infections are thought to result from direct contact with environmental reservoirs of C. atrobrunneum such as soil, and accordingly farmers or children may have greater susceptibility. [17]