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Aspergillus niger is a widely distributed filamentous fungus that is responsible for the spoilage of many foods. There are a few cases of its having caused disease in humans, but it is primarily a plant pathogen. This fungus is often found indoors and grows as black colonies. Known as black mold, it is often confused with the toxic black mold, Stachybotrys chartarum, that can infest water-damaged dwellings and cause severe symptoms in people.
Black mold is ever-present in soil and decaying plant matter, such as compost piles. Its spores are very common in the air. Healthy people can get sick from this fungus, if they breathe in a large quantity of the spores at once. The resulting disease can be a type of pneumonitis, or an inflammation of the walls — or the air sacs in the walls of — the lungs. This condition usually improves after several weeks of rest and treatment. It is also possible to get aspergillosis, a more serious syndrome of lung conditions, from breathing these spores.
People that are particularly vulnerable to aspergillosis are those that have compromised immune systems. This can be due to disease, like HIV infection. It can also be from medical treatments that suppress the immune system, such as those that prevent organ or bone marrow rejection. This disease, however, is usually caused by Aspergillus fumigatus.
One illness that aspergillus niger has been found to cause frequently in healthy people, is ear infection. This can result in pain and temporary hearing impairment. Severe cases can result in damage to the ear canal and typanic membrane, or eardrum.
This fungus is widely used industrially to produce a variety of organic compounds, including many types of enzymes. For example, it helps to produce the enzymes pectinase, alpha-galactosidase, and glucose oxidase, among others. Large amounts of the fungus are typically grown in giant vessels, known as fermenters, to produce a substantial quantity of the desired product.
There have been some reports of asthma induced by this fungus. In one case, a particular strain was being used industrially to alter molasses, to produce citric acid. A number of the workers involved developed asthma. The factor that caused the asthma appeared to be specific to the individual strain of fungus being used.
There is some debate, but it appears that aspergillus niger makes compounds known as mycotoxins. These are fungal compounds that are toxic to humans and animals. They are produced by some strains under particular growth conditions.
Aspergillus niger is a common food contaminant. It can grow on a range of crops, and is a particular problem on onions — both in storage and in the field. It also appears on stored grains, such as wheat and rice, and on legumes, like soybeans and peanuts. In lab studies, mice and chicks have died after being fed food contaminated with aspergillus niger, such as moldy soybeans, which presumably contained mycotoxins. Human food that is known to be prone to mycotoxin contamination is generally screened for its presence to ensure public safety.
Please tell the spore size of Aspergillus niger.