All About Microbiology

Microbiology is the study of small organisms also known as micro-organisms. The word micro meaning small. The main micro-organisms that are studied are fungi, bacteria and viruses.

Robert Hook was the first person to observe micro-organisms in 1666. He recorded the changing state of mould on fruiting bodies.


The most common micro-organism is fungi. Without knowing many people eat fungi every day, a mushroom is in fact a common example of fungus. Other examples include bread mould and yeast.

Fungus, unlike bacteria or virus is a eukaryote. This means that the cells within fungi have a nucleus within their nuclear envelope.

Fungi have both beneficial and harmful aspects. For example, yeast is a fungus which people use every day to bake. However, fungi can cause diseases such as potato blight which caused the famine in Ireland in the 1800’s. This resulted in the death of one million people.

Benefits of FungiDisadvantages of Fungi
Fungi can decompose – meaning they can break down dead material.Fungi can diseases and infections such as athlete’s foot
Fungi are used to make antibiotics such as PenicillinFungi cause food moulding causing food to be uneatable
Fungi are used to cook and bake withFungi can cause dry rot in wood



Bacteria is a single cell organism and cannot be seen with the naked eye. In order to see bacteria, you must use a microscope. Bacteria is one of the first organisms to live on earth. There aren’t many places where bacteria are not present. Bacteria can grow in soil, water, the air and also in and on plants and animals.


Bacteria is known as a Prokaryotic organism. This is the opposite to a fungus, as a prokaryotic organism does not have a membrane bound nucleus.

Almost all animals including humans need bacteria to survive. For example, bacteria are needed to produce vitamin B12, a vitamin that is a necessary component involved in the human metabolism.

There are both harmful and harmless forms of bacteria. As humans, our immune system forms a protective barrier to help our bodies fight against everyday bacteria. However, bacteria have caused diseases such as tuberculosis which kills millions of people per year.

TB In Sputum

Disadvantages of Bacteria

Benefits of BacteriaDisadvantages of Bacteria
Bacteria act as decomposers of plants and animalsBacteria can cause common and fatal illnesses such as food poisoning and TB
Bacteria can be used to produce antibiotics to fight bacterial infectionsBacteria can cause food to spoil e.g causing milk to go sour
Bacteria are used in the production of cheese and yogurtBacteria can cause tooth decay



Viruses are the smallest of all the micro-organisms. All viruses are parasites. This means that a virus can only live in or on another living thing. They need a host in order to survive and reproduce. Due to this a virus is neither a Eukaryotic or Prokaryotic organism. A virus cannot be Eukaryotic or Prokaryotic as does not possess the properties of a living organism without a host.

When a virus infects an organism, it rapidly produces thousands of identical copies of the virus within the organism.

Viruses can cause both common illnesses and fatal diseases. For example, the common cold is caused by a viral infection. However, viruses are also known to cause pandemics such as the flu pandemic, the AIDS pandemic and the Coronavirus pandemic which emerged in 2019.

Unlike bacteria and fungi, there are not many advantages to viruses. One advantage that can be noted is that some viruses can increase immunity against bacterial pathogens.

Microbiology worksheet