Aspergillus – Identifying The Most Common Kinds; Niger – Flavus And More

Today, we will work to better understand the fungi Aspergillus. Stick around to better understand the different types of Aspergillus, how it behaves as well as the good, bad, and ugly factors.

Aspergillus - Identifying The Most Common Kinds; Niger - Flavus And More

The Basics: What Is It?

Aspergillus is a particular genus of fungi that is made up of around 300 or so species of mold that we know of. It can be found in a wide array of environments worldwide, as their growth is typically subjective to water availability.

Thus, you probably wouldn’t find any in the desert.

The rate at which they are found to grow is also often determined by the temperature that is available where they are growing. Nonetheless, it has been shown in studies that Aspergillus can actually tolerate extreme conditions if everything else is ideal.

While some will reproduce sexually, a vast majority of aspergillus reproduce asexually, which means that they are usually referred to as conidial fungi.

They belong to the Fungi Kingdom, and the Ascomucota Phylum, he Eurotiales Order, and the Trichocomaeceae Family, with their genus being Aspergillus.

Most have been noted to be terricolous, this means that they are often found in land and soil.

They were discovered back in the 1720s decade, and since then have become very crucial in human health, as well as agriculture, but also in biological science. They also have other applications as well.

They are a fungi that are known to reproduce asexually for the most part, via the production of spores. Their spores are referred to as conidiums.

The Behavior Of Aspergillus

Aspergillus are often found in many aspects of nature, and their spores are largely found in the air.

They are also largely known as being saprophytes as they obtain the nutrition that they require from decaying or dead matter, however they can also be somewhat pathogenic to animals and humans, and some may also affect and harm plants as well.

As they lack a chlorophyll, they are unable to produce their own food like plants can, and are dependent on materials in their environment to gain nutrition.

This is wherein it is worth noting that Aspergilli are actually not able to absorb any organic matter in their environment either.

This is why you will find that they often release a multitude of different enzymes, including ones such as amylase which are capable of being able to break down materials into simple compounds that the aspergilli can then absorb through their vegetative hyphae.

They also release very high amounts of these enzymes to enhance the decay of any and all organic matter in their immediate surroundings, and increase the availability of their food source as needed for their steady growth and reproduction.

Generally they will reproduce via their spores, which are known as conidium, or fungi spores.

Once a spore lands in a suitable environment, with the ideal warmth, moisture, and nutrition available, they will start to germinate where they can create even more hyphae that will end up forming a mycelium.

The hyphae will allow them to spread, grow and continue the reproductive cycle across the surface of their chosen environment.

This means you could summarize the life cycle of an aspergillus as starting as a spore, which germinates, then forming a hyphae and elongating, then branching out to form the mycelium, and finally creating spores once more, and repeat.

The Aspergilli’s hyphae will develop into reproductive and vegetative hyphae.

The vegetative hyphae will serve to be able to absorb the nutrients in their food, meanwhile their reproductive hyphae will develop even more to be capable of producing spores.

The Types Of Aspergillus

The Types Of Aspergillus

There are a plethora of species that fall under the Aspergillus genus, we would like to share some of the most found fungi that tend to fall into this genus with you. You may even recognize some!


Let’s start off by looking at Aspergillus Niger, it typically exists as saprophytes, meaning that they usually get their nutrients from a wide variety of dead and decaying material, usually such as leaves, fruits and such other vegetation that will likely die in their environments.

Therefore, they will also be often found as part of the decaying process of many food products as their source of nutrients and vegetation is available pretty much anywhere

The Aspergillus Niger are, therefore, very widely distributed, and it is common to find them in many different geographical locations. That being said, they are also well known for being more present in areas that have higher temperatures.

Research has come to the conclusion that the black spores that Aspergillus Niger has aids this mold in protecting them from the radiation of the sun, thus allowing them to thrive in very warm areas, where others would not.

Understanding Aspergillus Niger

Much like some others, the Aspergillus Niger are a filamentous fungus, meaning that they usually create filaments i.e. hyphae, and therefore are similar in structure to a plant.

If you were to view an Aspergillus Niger under a microscope you would note that it has smooth and colorless conidiophores as well as notable spores.

Upon closer inspection you would note that the conidial heads of this particular organism tend to be globose and a dark brown in shade that look to divide into a variation of columns as the Niger ages.

In comparison to other types of the Aspergillus, the Aspergillus Niger tends to have dark, or a dark brown spore which they produce from their conidial heads.

This is something that has only ever been seen with the Aspergillus Niger, and no other Aspergillus.

Their dark spores are used in microscopy to distinguish this type of Aspergillus from others. It is a distinguishing feature that defines it from others in its genus.

Aspergillus Niger Reproduction

The Aspergillus Niger is a typical ascomycetous fungus, meaning that it is classified as an Ascomycota phylum, which is also commonly referred to as being a Sac Fungi. Therefore, it produces spores within its sacs, and it reproduces asexually.

It is much like some Aspergillus Nidulans, as colonies of Aspergillus Niger which have been exposed to oxygen in suitable growth conditions will often form their own reproductive and vegetative hyphae.

The vegetative hyphae will absorb nutrition from dead or decaying matter and the spores will be produced from the tip of their reproductive hyphae.


Much alike to Aspergillus Niger, Aspergillus Flavus are also a saprophyte, they can also be found in soil where they will easily obtain their required nutrients from dead or decaying matter. Typically, Aspergillus Flavus are seen as being a heavy nuisance for farmers as they often infect, and thus contaminate crops and seeds.

Aspergillus Flavus are often divided into two particular groups, this is based upon their morphology. Let’s look at them

The S Strain

Of Aspergillus Flavus you would find the S strain, this is also often referred to as Group I, and it has a sclerotia, which is a hardened mass of mycelium, which is smaller than 400 millimeters in size, this is also its identifying characteristic.

This is a strain that has been shown to often produce a very high constant content of aflatoxin which will often affect crops and animals both.

The L Strain

The L strain of Aspergillus Flavus is different to the S strain as it has a sclerotia which is even bigger than 400 millimeters in diameter.

This is a strain that also produces aflatoxins, but the amount it does produce can vary from extremely high to extremely low, and therefore it is not consistent like the S strain is.

Often aflatoxins that are produced by an Aspergillus will usually cause serious intestinal issues or liver cancers in humans.

Aspergillus Flavus is actually the 2nd highest cause of Aspergillosis in humans who have a weak immune system, Aspergillosis is a lung infection caused by this fungus.

Much like many other types of Aspergillus, the Flavus also produces its own hyphae, which includes both reproductive and vegetative hyphae. In the vegetative hyphae the Flavus will produce enzymes which have the job of breaking down its food materials into forms that can be absorbed.

Although this organism has been known to produce spores asexually like many other Aspergillus, it is also one of the few types that has the genetic diversity to be a result of sexual reproduction in which ascospores are produced in the sclerotia of the Flavus.

Understanding The Aspergillus Flavus

To understand the Aspergillus Flavus, let us look at some of its morphology. Its main parts of its morphology include:

  • Conidia
  • Metula
  • Phialide
  • The Stipe
  • Vesicule

If you were to view the Aspergillus Flavus underneath a microscope, you would note that it appears to have a conidial head which radiates whereas the conidiophores will look to be rough.


Then there is the Aspergillus Fumigatus. This is one of the most found Aspergillus as it is frequently found in a majority of environments.

One of its most defining features that distinguishes it from other forms of Aspergillus is that it is very successful at surviving high temperatures.

This is also the reason that it is more prevalent in the world.

It also exists as a saprophyte, and it plays a very important part in the cycle of both nitrogen and carbon in the natural world.

As it is highly prevalent, the spores of the fungi are in very high concentrations in the air, which can present a very serious risk of health problems for those who have poor immune systems.

In comparison to other species of the Aspergillus genus, the Fumigatus has been found to also be the most prevalent pathogen amongst those who have compromised immune systems.

This is a fungi which is capable of surviving from 37 degrees Celsius, although the conidia can survive up to 70 degrees Celsius!

The Aspergillus Fumigatus is a filamentous fungus which is able to use asexual or sexual means to reproduce. Although no one quite understands the sexual means of reproduction just yet!

In its asexual reproduction, however, the conidia are produced via a mitotic division, and in this mitotic division which happens in the conidophore vesicle, they will be released by any disturbance of the surrounding environment.

This makes the spores rise in a high concentration into the air, into which they can be inhaled, which can cause health complications for those who may have a compromised immune system.

The asexual reproduction of the Aspergillus Fumigatus will take place in places where the mycelia doesn’t have any interaction with another haploid mycelia.

Understanding The Aspergillus Fumigatus

Let’s take a look at some of the different morphological characteristics you can find in the Aspergillus Fumigatus. Here are some facts about its morphology:

  • The Aspergillus Fumigatus can produce spores which are between 200 and 400 millimeters in size.
  • The colors of their stipes is usually gray around the apex.
  • The Aspergillus Fumigatus will often have a smooth surface.
  • They can often have a small and columous globus.
  • The conidia surface is usually smooth or spinose.


Let’s finish off by looking at the Aspergillus Nidulans, otherwise known as the Emericella Nidulans, which is one of the most researched Aspergillus.

The reason for its heavy studying is that it is often found to be very closely related to a vast majority of other species of Aspergillus as well as having a very well organized genetic system.

This means that it is very important in much medicinal and industrial research.

Although it is the main subject of many important studies, the means of its reproductive strategies are still yet to be properly understood.

That being said, a varying number of studies have shown that it is capable of using sexual and asexual means to reproduce.

Unlike the other types of Aspergillus, the ones that cause foods to spoil by enhancing the process of decay, the Nidulans do not always cause spoilage.

It is capable of growing at high temperatures, but it is also known to produce a particular toxin, known as mycotoxin which can end up resulting in some health issues among people who may have a compromised immune system.

Why Is Aspergillus Important?

Now we want to have a look at why Aspergillus is important. There are two primary reasons.

Firstly, its carbon and nitrogen cycle.

In response to it needing nutrients, studies show that Aspergillus Fumigatus is able to sense the presence of nitrogen and carbon materials, which results in the Aspergillus breaking it down, especially in non-wood based plants in order to obtain the nutrients it needs to absorb.

This is shown to be a very important process in the overall cycle in nature of both nitrogen and carbon.

Then, we must also consider enzymes as well. Aspergillus is able to obtain the nutrients that they need by releasing enzymes that will break down their food materials into smaller pieces which they can more easily absorb.

This is something that has been shown to be very beneficial in many different industries in which these particular organisms are used for their enzymes and how they break down particular proteins and other compounds in nature.

One of the most used of these organisms is Aspergillus Oryzae which is often used to ferment various different products.

There are some other very important uses of Aspergillus as well, these include food preservation, although it may sound strange, as it has a capacity to decompose, Aspergillus Niger is often also used to preserve different food products from spoiling.

As well as this, citric acid is a part of this as Aspergillus Niger is used to be able to produce citric acid as well.

What Is Bad About Aspergillus?

There are some things that are good about Aspergillus, but not all is good. There are some bad ones as well. Here are some of the disadvantages.

Firstly food spoilage. With the Aflatoxins that are produced by some Aspergillus that can spoil different crop seeds being the biggest issue. These are dangerous toxins which can cause health issues as well as death if they are consumed.

There are also enzymes that are produced by Aspergillus that enhance the decaying of fruits and other food types as well.

And of course, let us not forget about the animal and human infections that Aspergillus can cause. Aspergillus and the spores that they produce can have some very negative health effects when they are inhaled.

While aflatoxins can affect healthy or unhealthy humans and animals, the Aspergillus and their spores can have deadly negative consequences on those who have poor immune systems.

One of the most common conditions caused by Aspergillus is ABPA (Allergic Bronchopulmonary Aspergillosis) which is a condition in which the immune system exaggerates its response to the Aspergillus fungus and is often found in those who have asthma or cystic fibrosis.

This is what you might call an allergy to mold, although for those with weak immune systems it can be much worse!

To Conclude

Overall, Aspergillus is a unique organism in our world that has many upsides and just as many downsides, it can be useful in the production of products and useful in many ways to our scientific advancements, however, it does also pose many health risks.

Aspergillus Niger is one of the most serious health risks, as it is more commonly known as ‘black mold’ or ‘toxic mold’. It is effective in science and some economical aspects, but it is not something that you want to find in your home, as it is notoriously hard to get rid of.

Jennifer Dawkins

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