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Aspergillus ustus

Microscope

Anamorph
Aspergillus ustus (Bainier) Thom & Church

 
Generalities

Aspergillus ustus is among the most ubiquitous soil species but it is more frequently found in tropical and subtropical areas.

Its presence indicates a deficiency of the soil because it is highly destructive and grows where other species are unable to grow.
It is the main contaminant of cultivated soils but it occurs on other habitats:
  • forests
  • sea
  • salty grounds and alkaline environments
  • deserts
  • unusual habitats such as the recently defrosted soil in Alaska
Besides, it has been isolated from various substrates such as:
  • rubber
  • cardboard
  • plants (lupin, lucerne, food producing cultures [beetroot, cotton, sugar cane, potato ...])
  • synthetic materials (plasticizers)
  • paper
  • feathers of living birds
  • food products (refrigerated products, dried fruits, nuts, cheeses, citrus fruits, seeds and cereals…)
A. ustus is not pathogenic but can be found in some skin infections in immunodeficient patients.
Herbicides containing aniline bases are metabolized with aniline ions and/or chloride ions as degradation products.

 
Substrates
 
Toxins
 
Standards

    It is a reference species for the standard NF X41-517.

 
Description and growth

On Malt-Agar growth medium (MA) (pH 6.5) – Velvet-like colonies, olive-green to moss-green in colour with deep concentric grooves ranging from dark green to a lighter green hue. The conidiophores are brown, smooth-walled and can be as long as 40 µm. The conidia heads are columnar when mature with hemispherical or globose and generally pigmented vesicles. The conidia are 3.2 to 4.5 µm in diameter and are globose to rough. Presence of hyaline Hülle cells irregularly elongated and scattered in the colony. The pH of the medium is not modified by the species (final pH 6).

 



recto - 26°C

verso - 26°C

On Czapek growth medium (pH 5.5) – Moderate growth colonies, velvet-like but less dense than on other media, brown-green in colour alternating with lighter concentric areas. The growth of the species basidifies the medium (final pH 8).



recto - 26°C

verso - 26°C

On CYA growth medium (pH 5.5) – fast growing colonies with a moss-green and velvet-like thick thallus showing concentric lines and light edges. Possible emission of a yellowish pigment. The species does not modify the pH of the medium (final pH 6).



recto - 26°C

verso - 26°C





A. ustus ne se développe pas à 37°C.


Development on different materials.

A. ustus develops far better on parchment and newspaper than on other materials. Its growth on edition paper is less fast and is very weak on cotton fabric. It is moss-green on all studied materials.



Aspergillus ustus sur textile

 
Biology

Non-xerophile species.

A. ustus lives in soils at pH 6-7.5.

A.ustus is capable of sporulating without any light but the production of Hülle cells is totally photosensitive. Minimal, optimal and maximal temperatures for the growth respectively are of 6-7°C, 25-28°C and 41-42°C. A 25-minute exposure at 62°C totally kills the species.

The use of sugar and the degradation of starch or proteins are optimal at 25°C, weak at 15°C, and still good at 35°C.

The DNA analysis shows that the strain has a 53% GC content.

A. ustus is highly CO2 sensitive.



 
Biochemistry

A.ustus uses as carbon sources:
•  fructose
•  lactose
•  paraffin
•  polyvinylacetate
•  simazine
and (NH4)2SO4 as nitrogen source.

Synthesized compounds:
•  kojic acid
•  ustic acid
•  austamide
•  austdiol (gastro-intestinal toxin)
•  austines
•  autocystines
•  dextran (production inhibited by the presence of other carbon sources and some sugar alcohols)
•  pyridoxine
•  riboflavin
•  sterigmatocystine

It is able to degrade starch as well as cellulose under different forms.

A.ustus is able to inhibit the growth of some micro organisms such as Staphylococcus aureus and of microscopic fungi such as Sporothix schenckii, Scopulariopsis brevicaulis, Candida albicans and Sclerotinia sclerotiorum.
 



 
Bibliography

Botton B, Breton A, Fèvre M., Guy Ph. Larpent JP, Veau P (1985) Moisissures utiles et nuisibles. Importance industrielle. Ed. Masson, p 117, 118, 216, 218.

Domsch KH, Gams W, Anderson T-H (1993) Compendium of soil fungi, vol. 1, IHW-verlag Pub., 117-119.

Pitt JI, Hocking AD (1999) Fungi and food spoilage. Second edition. A Chapman and Hall Food Science Book, Aspen Publication, Gaithersburg, Marylan, 407-409.

Rabie CJ, Steyn M, van Schalkwyk GC (1977) New species of Aspergillus producing sterigmatocystin. Appl. Environ. Microbiol. 33 (5), 1023-1025.

Ricci RM, Evans JS, Meffert JJ, Kaufman L, Sadkowski LC (1998) Primary cutaneous Aspergillus ustus infection : second reported case. J. Am. Acad. Dermatol. 38 (52), 797-798.

Samson RA, Hoekstra ES, Frisvad JC. Filtenborg O (1996) Introduction to food-borne fungi. Fifth edition. Centralbureau voor schimmelcultures, Baarn, Delft, 78.

Stiller MJ, Teperman L, Rosenthal SA, Riordan A, Potter J, Shupack JL, Gordon MA (1994) Primary cutaneous infection by Aspergillus ustus in a 62-year-old liver transplant recipient. J. Am. Acad. Dermatol. 31 344-347.

Subramanian CV (1983) Hyphomycetes : Taxonomy and Biology. Academic Press Inc., p. 312, 341, 343, 345, 354, 392, 399, 400, 405.