Observing Mold Under The Microscope

There are many different types of fungi which can be observed under the microscope, one of which includes mold. Molds are a natural part of our environment, with the capability of being found in most places where oxygen and moisture are present.

Observing Mold Under The Microscope

Belonging to the fungi kingdom, which contains an excess of 99,000 different species, molds are most genetically similar to yeasts.

They break down dead organic materials which are sources of energy using enzymes. With mold being so abundant and easily grown, it is an ideal specimen to observe under the microscope. Below we look at how mold can be observed by a microscope. 

The Fungi Kingdom

The fungi kingdom comprises 144,000 known specimens. This includes mold, yeast, smuts, mildews and mushrooms. They are the most abundant organisms found on Earth and hold significant importance in medicine. 

Fungi are known as eukaryotic organisms, which means that their cells contain a nucleus and also membrane-bound organelles. They digest organic matter and absorb it through their mycelia. 

Fungi have been an important part of human life for decades, as well as their ability to form loaves of bread from yeast, and berries to wine, they have also played a vital role in expanding our knowledge of biology.

During the 1940s, scientists who studied the mold Neurospora developed a one-gene-one-enzyme theory, becoming the fundamental point of our knowledge of genetics. 

The Science Of Mold

Mold is a heterotrophic fungus, which means that it cannot create its own food. Molds gain nutrients from natural substances, which they absorb.

They are made of filaments which appear grass-like under a microscope, these are called their hyphae. These hyphae can grow very long, which is what differentiates them from yeasts, which have no hyphae.

The hyphae allow them to spread over the items they are absorbing. 

The Differences Between Mold And Fungi

Fungi can take several different forms, be that yeast, molds containing hyphae, or macroscopic mushrooms with sexual organs.

Some types of fungi can also coexist as both molds and yeasts, making them dimorphic. They alter according to changes in temperature. 

Molds, as opposed to other kinds of fungi, have hyphae filaments. The aggregation of the hyphae as a network makes up the mycelium. 

Fungi are aerobic organisms with yeast being anaerobic.

All different forms of fungi will absorb carbon through digestion and consist of parasites, saprophytes, and commensal. Molds are heterotrophic and aerobic organisms.

The Reproduction Of Mold

Another thing which distinguishes mold from other fungi is how they reproduce. Molds reproduce either sexually or asexually to produce spores. These will have the appearance of seeds.

To grow, molds require water along with other conditions such as temperature, light and food sources. 

The sexual reproduction of mold happens when two different hyphae are mated together, resulting in the production of spores. Asexual reproduction, on the other hand, happens when mitosis or meiosis occurs.

These are the two types of cell division which allow molds to reproduce. 

When reproduction occurs, spores are released and scattered throughout the environment.

Spores can endure fairly extreme conditions, with the ability to survive both high heat and cold temperatures. They can be transported by air and water to form in new areas. 

How To Observe Mold Under The Microscope

Preparing The Specimen

Safety note: When conducting this experiment, make sure to wear gloves.

The easiest way to observe mold under a microscope is to simply grow it yourself. This is best done through a food item such as a piece of bread. Preservative-free slices of bread will work best.

You can also use fruits, which also have a high growth rate of mold. Molds most commonly observable on food items include Rhizopus, Neurospora, Aspergillus and Penicillium. 

To speed up the growth of mold on your food, begin by leaving it in the open air for at least 30 minutes, this is so that your food becomes exposed to contaminants.

After this, place it in a ziplock bag and place a small amount of water over it to create dampness. Put it in a dark warm area. After five days, mold should have formed on the food. 

What You Will Require

  • The specimen sample
  • Glass slide
  • Coverslip
  • Microscope
  • Gloves
  • Dropper
  • Methylene blue


  1. Place a drop of methylene blue on the center point of the slide using a dropper. Water can replace the use of methylene blue if there is none available. It is recommended, however, that methylene blue is used for this as it will enhance the visibility of the specimen.
  2. Use a toothpick to scrape the mold off of the food item and place it carefully on the methylene blue. 
  3. Grab the coverslip, which will need to be placed on an angle to the slide, so that the edge touches the methylene blue. Bring it down slowly over the droplet so that it covers the specimen fully, taking care not to trap any air bubbles within. 
  4. Blot any excess water with a paper towel. 
  5. Place the slide carefully on the microscope to begin viewing. Start with a low power before moving on to high power.   

Issues When Observing Mold Under A Microscope

Because there are so many different kinds of mold which can grow, the appearance of the mold which you observe will be dependent on that particular variant.

When following the steps outlined above, one should have little difficulty in observing the specimen. Some issues, however, can arise depending on the variant of mold that is under observation. 

Some types of mold can disintegrate as soon as they are mounted on the slide. Species of Cladosporium, Monilia, and Alternaria, all of which can be found growing on food items, have spores which are connected by incredibly fragile chains.

These can break apart as they are moved through the air. 

Different Types Of Mold

Different Types Of Mold


Acremonium mold takes its name from the English word ‘acrimonious’, which is defined as being angry or resentful.

There are 150 known species of acremonium, and they commonly grow in the home in areas such as the bathroom, laundry room, and basements, essentially, where excessive water may be present.

They can cause ill health by affecting the skin through cuts and scrapes.


There are over 500 species of this mold, it can make an appearance with either black, green or brown spots.

It is commonly found on wallpaper, windowsills, fabrics, wood and floors. It is a common mold which can cause poor health, especially those with preexisting conditions such as asthma. 


Stachybotrys are one of the most widely recognized types of mold, as they are commonly referred to as black mold. They have an overall slimy appearance and can be toxic to humans.

It grows on material which has a high cellulose content, such as paper, gypsum board or fiberboard. Consistent moisture is required for its growth. 


These molds grow at an elevated speed. Consisting of around 50 species, they grow at temperatures below 98º F (37º C).

It begins with an appearance of being white and fluffy, before altering to a gray. It tends to live in furniture such as carpets, upholstery, and mattresses. Flood damage is a common cause for this kind of mold.

What Magnification Do You Need To See Mold?

To study fungal spores in general you will need fairly significant magnification. A microscope which is capable of at least x 400 magnification will usually suffice.

Molds can usually be viewed at a mere 100x magnification, whereas bacteria are incredibly difficult to view unless viewed at 1000x magnification.

What Does Mold Look Like Under The Microscope?

How mold looks under the microscope depends on which type of mold you are observing. Typically, mold spores are described as being black, smooth and round in appearance when viewed under the microscope.

They will be distinguishable because they always have a smooth shape, rather than jagged, misshapen, irregular particles. 


Mold is a unique member of the fungi family. Being the only to contain hyphae, it is easy to distinguish from other kinds. Ubiquitous in nature, it is a widely found type of fungus, making it ideal for microscopic observation.

Because there are many types of mold, the type which will be seen under the microscope varies. 

Jennifer Dawkins

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