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Aspergillus ochraceus MUT 2036
Conidial heads and droplets of exudate on malt extract agar (MEA). Inset: 5-day old colonies (counter-clockwise from left) on Czapek yeast extract agar (CYA), yeast extract sucrose (YES), and MEA media. Photo credit: Massimo Ferrara from CNR-ISPA.

Aspergillus ochraceus K. Wilh., Beitr. Kenntn. Aspergillus: 66. (1877). Series Circumdati belongs to the subgenus Circumdati section Circumdati.

Aspergillus section Circumdati (also formerly called Aspergillus ochraceus group) includes species with biseriate conidial heads in shades of yellow to ochre and is responsible for production of several mycotoxins harmful for animals and humans, such as ochratoxin A (OTA), penicillic acid, xanthomegnin, and viomellein. Some species of the section are useful for the biochemical transformation of steroids and alkaloids, or as sources of proteolytic enzymes; while other species produce several promising anticancer compounds.

Aspergillus ochraceus colonies spread en masse with pale yellow to light yellow conidia that are generally finely rough-walled and small (subglobose, 2.5–4 × 2.5–3.5 μm) and usually with white mycelium and purplish to brown sclerotia. Extrolites include aspergamides, aspyrone, circumdatins, mellein, orthosporin, penicillic acid, and xanthomegnin. Aspergillus ochraceus was the first fungus from which OTA was isolated and took its name. OTA is a highly harmful metabolite classified in 1993 by the International Agency for Research on Cancer (IARC) as a possible human carcinogenic toxin (group 2B). However, from 2004, the OTA producing strain was re-identified as the new species A. westerdijkiae, and A. ochraceus became less relevant for OTA contamination of food than new highly producing species A. westerdijkiae and A. steynii.

This fungus is reported to be common in a wide range of terrestrial habitats such as soil, agricultural and stored foods (mainly cereals, coffee and cocoa), but also in marine environments. The strain Aspergillus ochraceus MUT 2036 was isolated from sea cucumber Holothuria polii from a rocky coast of Tabarka peninsula in Tunisia, Africa (Marchese, et al., 2020). It has been reported as a mycotoxin producer and was investigated for the presence of mycoviruses in relation to ecological and biochemical traits (Nerva et al., 2018; Nerva et al., 2019).

References:

  • Marchese P, Garzoli L, Gnavi G, O'Connell E, Bouraoui A, Mehiri M, Murphy JM, Varese GC. Diversity and bioactivity of fungi associated with the marine sea cucumber Holothuria poli: disclosing the strains potential for biomedical applications. J Appl Microbiol. 2020 Sep;129(3):612-625. doi: 10.1111/jam.14659. Epub 2020 Apr 21. PMID: 32274883.
  • Nerva L, Chitarra W, Siciliano I, Gaiotti F, Ciuffo M, Forgia M, Varese GC, Turina M. Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus. Environ Microbiol. 2019 Jun;21(6):1957-1968. doi: 10.1111/1462-2920.14436. Epub 2018 Oct 25. PMID: 30289193.
  • Nerva L, Forgia M, Ciuffo M, Chitarra W, Chiapello M, Vallino M, Varese GC, Turina M. The mycovirome of a fungal collection from the sea cucumber Holothuria polii. Virus Res. 2019 Nov;273:197737. doi: 10.1016/j.virusres.2019.197737. Epub 2019 Aug 31. PMID: 31479695.