Fungal Infections

Species/common name:

Aspergillus niger

Teleomorph:

Sterigmatocystis nigra

Several closely related and cryptic species, such as A. awamori  and A. tubingensis.

Natural habitat

A. niger is primarily found within soil.

Geography

Worldwide distribution. It has been cultured from numerous habitats.

Frequency

Common in otomycosis (fungal ear infections). Occasionally found in aspergillomas (diabetics) and invasive pulmonary aspergillosis but this species rarely disseminates through the body.

Diseases

Aspergillosis refers to infection by any of the Aspergillus species. Infection can be limited to the lungs (pulmonary) or spread throughout the body (disseminated Aspergillosis) in more severe cases. Aspergillus niger is most often associated with:

1)      Otomycosis

2)      Chronic pulmonary aspergillosis and aspergilloma

3)      Asthma exacerbation and severe asthma with fungal sensitization (SAFS)

4)      Allergic bronchopulmonary aspergillosis (ABPA)

5)      Aspergillus bronchitis and invasive tracheobronchitis

6)      Invasive (pulmonary) aspergillosis

7)      Disseminated aspergillosis

Culture peculiarities

Cottony appearance; initially white to yellow and then turning black. Made up of felt-like conidiophores. Reverse is white to yellow. In microscopy, the conidial heads are radiate with conidiogenous cells biseriate. Conidia brown.

Antifungal resistance (intrinsic and acquired)

One study showed itraconazole resistance in 33% of isolates. Cross-resistance has been noted but is unusual.

Biosafety level 1

This fungal species may be managed in a laboratory with safety containment level 1.

Industrial use:

Citric and gluconic acids are produced industrially through A. niger. Some useful enzymes are produced during fermentation including glucoamylase (used for the manufacturing of corn syrup) and pectinases (for wine and cider clarification). A. niger is used for the production of glucose oxidase, an enzyme used in glucose biosensors.

Images

Aspergillus niger, as grown on Sabouraud (SAB) agar.

A niger

Aspergillus niger, on Malt extract agar

 Microscopy appearance of A. niger

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