Aspergillus terreus

Aspergillus terreus.jpg
Conidial heads
Aspergillus terreus, also known as Aspergillus terrestris, is a fungus (mold) found worldwide in soil. Although thought to be strictly asexual until recently, A. terreus is now known to be capable of sexual reproduction. This saprotrophic fungus is prevalent in warmer climates such as tropical and subtropical regions. Aside from being located in soil, A. terreus has also been found in habitats such as decomposing vegetation and dust. A. terreus is commonly used in industry to produce important organic acids, such as itaconic acid and cis-aconitic acid, as well as enzymes, like xylanase. It was also the initial source for the drug mevinolin (lovastatin), a drug for lowering serum cholesterol.

A. terreus can cause opportunistic infection in people with deficient immune systems. It is relatively resistant to amphotericin B, a common antifungal drug. Aspergillus terreus also produces aspterric acid and 6-hydroxymellein, inhibitors of pollen development in Arabidopsis thaliana.

A. terreus is brownish in colour and gets darker as it ages on culture media. On Czapek or malt extract agar (MEA) medium at 25 °C (77 °F), colonies have the conditions to grow rapidly and have smooth-like walls. In some cases, they are able to become floccose, achieving hair-like soft tufts. Colonies on malt extract agar grow faster and sporulate more densely than on many other media.

A. terreus has conidial heads that are compact, biseriate, and densely columnar, reaching 500 × 30–50 µm in diameter. Conidiophores of A. terreus are smooth and hyaline up to 100–250 × 4–6 µm in diameter. The conidia of A. terreus are small, about 2 µm in diameter, globose-shaped, smooth-walled, and can vary from light yellow to hyaline. Unique to this species is the production of aleurioconidia, asexual spores produced directly on the hyphae that are larger than the phialoconidia (e.g. 6–7 µm in diameter). This structure might be influential in the way A. terreus presents itself clinically as it can induce elevated inflammatory responses.

This fungus is readily distinguished from the other species of Aspergillus by its cinnamon-brown colony colouration and its production of aleurioconidia. A. terreus is a thermotolerant species since it has optimal growth in temperatures between 35–40 °C (95–104 °F), and maximum growth within 45–48 °C (113–118 °F).

A. terreus, like other species of Aspergillus, produces spores that disperse efficiently in the air over a range of distances. The morphology of this fungus provides an accessible way for spores to disperse globally in air current. Elevation of the sporulating head atop a long stalk above the growing surface may facilitate spore dispersal through the air. Normally, spores in fungi are discharged into still air, but in A. terreus, it resolves this problem with a long stalk and it allows the spores to discharge into air currents like wind. In turn, A. terreus has a better chance to disperse its spores amongst a vast geography which subsequently explains for the worldwide prevalence of the fungus.

This page was last edited on 17 February 2018, at 08:33.
Reference: under CC BY-SA license.

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