What is a Microorganism?

In the previous section, we looked at living cells, the basic unit of life on Earth. We learned that some living things contain millions of cells and that others contain only 1 cell. In this section, we will focus on living things containing only 1 (or sometimes only a few) cells.

A Microorganism is a living thing that can only be observed using a microscope. Most microorganisms contain only 1 cell. There are millions of different types of microorganisms, many have a positive effect on our lives but some can have negative effects, such as cause diseases.

Types of Microorganisms

There a millions of different microorganisms on Earth, but all can be described in four main groups:-

  1. Bacteria

  2. Viruses

  3. Fungi

  4. Protists


The diagram below shows the three main shapes of bacteria:-

The audio file below is a track from Jeff Wayne's War of the Worlds, based upon H.G. Wells classic novel.

As can be seen from the above audio clip, bacteria are microorganisms which can cause diseases. However, bacteria have many more functions, most of which have nothing to do with us at all!

The function of bacteria include:-

  1. Helps plants to absorb Nitrogen from the soil.

  2. Break down cellulose in the stomach of certain animals to allow them to digest plant material.

  3. Causes dead organisms to decay, returning their nutrients to the environment.

  4. Used to create Insulin, a hormone needed by people with Diabetes.

  5. Digest waste products in sewage, as part of Water Purification.

  6. Some bacteria give off Oxygen as waste, this was the source of Oxygen in the atmosphere before plants existed.

There are thousands of other beneficial things that bacteria do, without which the Earth would look very different!

Diseases caused by bacteria include:-

  1. Food Poisoning

  2. Cholera

  3. Typhoid

  4. Pneumonia


The diagram below shows the four main shapes of viruses:-

Viruses are much smaller than bacteria. Viruses are so strange that scientists are unsure if they qualify as being a living thing! Unlike most living things, viruses cannot reproduce on their own, they can only reproduce inside other cells.

To reproduce, the virus enters a cell, then they take control of the cell, forcing it to make thousands of copies of the virus. Eventually the cell then bursts open, releasing the new viruses which can go on to infect other cells.

Diseases caused by viruses include:-

  1. Flu

  2. Measles

  3. Mumps

  4. HIV and AIDS

  5. Chicken Pox

The video below shows a detailed description of how viruses attack living cells.


The diagram below shows the two main types of Fungi:-

Fungi are neither plants nor animals, but a class of organisms all of their own. Most people can recognise the multicellular fungi (mushrooms and toadstools), but most do not realise that the moulds that grow on food are also fungi. Fungi specialise in decay, and are vital in the decomposition of dead material, especially wood.

Like bacteria, fungi have many more functions than causing diseases, most of which have nothing to do with us at all!

The functions of fungi include:-

  1. Causes dead organisms to decay, returning their nutrients to the environment.

  2. The fungi Yeast is used in baking to make Bread rise and in brewing to ferment sugar to make alcohol.

  3. Fungi can be used to make protein for meat substitutes (Quorn).

  4. Certain types of fungi can be eaten, but you should NEVER eat an unidentified mushroom, as some are highly poisonous.

  5. Fungi can kill other microorganisms such as bacteria, by creating chemicals called antibiotics.

There are thousands of other beneficial things that fungi do, without which the Earth would look very different!

Diseases caused by fungi include:-

  1. Athlete's Foot

  2. Ringworm

  3. Thrush

  4. Fungal Nail Infection


The diagram below shows the three main types of protists:-

Like fungi, protists are neither plants nor animals, but a class of organisms all of their own. They all are single-celled organisms, and display similarities with animals, plants and fungi, but are too different to be counted in those groups. The plant-like protist Algae is responsible for the creation of over half the Earth's Oxygen.

Diseases caused by protists include:-

  1. Malaria

  2. Giardiasis

  3. Sleeping Sickness

Growing Microorganisms

Colonies of microbes can be grown rapidly on Agar (a jelly-like food source) in Petri dishes. The process of growing microbes is known as "culturing microbes".

Microbes require a source of food, water, oxygen and an appropriate temperature to grow.

Aseptic Techniques

In order to grow microbes safely, aseptic techniques must be used, so that only the microbes required will be grown.

Aseptic means "no infection", but in this context it means no contamination with unwanted microorganisms.

We can prevent contamination by:-

  1. Disinfecting the work space before starting.

  2. Washing our hands.

  3. Using a bunsen next to the kit creating an updraft to prevent microbes falling onto the petri dish from the air.

The step by step process below should be followed when culturing microbes:-


Using microbes has many uses within industry, creating millions of jobs around the world, in a range of ways. Some of the uses of microbes are:-

  1. Biological breakdown of sewage - Bacteria used to break down waste as part of sewage treatment.

  2. Biological breakdown of oil spills - Bacteria used to break down oil reducing the impact of oil spills.

  3. Manufacturing of Insulin - Insulin, a vital treatment for Diabetes, is creating using transgenic bacteria.

  4. Bread making - The fungi Yeast is used to create Carbon Dioxide to make bread rise.

  5. Alcohol production - The fungi Yeast is used to break down sugars creating alcohol as a waste product.

  6. Nematode treatment - Specific species of protists can be applied to garden plants to kill pests or diseases.


As a Biotechnologist, you would use your biology knowledge to come up with products and processes that improve our health, our food and our world.

Your work would depend on your specific field, such as developing treatments for the genetic causes of disease or producing medicines using techniques such as cell culture and genetic modification. You could also develop micro-organisms and plants to clean polluted land or water, create renewable sources of energy or produce environmentally-friendly materials for industry.



A Career as a Biotechnologist

Salary: from £25,000 to £60,000 per year

Biotechnologist working hours: 35 and 40 hours a week. This may include shifts, nights and weekends because many of the processes involved in research and industry need continuous monitoring.

Typical entry requirements: A degree (SCQF level 9/10) in a subject such as biotechnologies, biological science, microbiology, or chemistry.

Most undergraduate courses ask for at least four Highers at B or above (SCQF level 6). Some universities may require AABB (first sitting) for entry.

The University of Dundee offers a BSc Life Sciences course with only requires two Highers at B including Biology or Chemistry and one other subject; this course has been developed for those with high academic potential who experienced disadvantage.

Skills required:

  • Taking initiative

  • Sorting

  • Attention to detail

  • Understanding

  • Analysing

  • Working with technology

  • Researching

  • Observation

  • Problem solving

The Wonder of Yeast

Yeast is the earliest example of Biotechnology. Yeast has been used as long as farming has existed, since prehistoric times. Yeast is naturally occurring and easy to use, allowing prehistoric farmers to create two very important products, Bread and Beer.

Yeast is a single-celled member of the fungi family and can be found naturally all over the world, in over 1500 different species. It is the Yeast's respiration process and waste products that make it so useful.

The following formula describes the respiration of Yeast:-

It is the two waste products, Carbon Dioxide and alcohol, that are useful to us.

Bread Making

Yeast is essential in making bread rise. When Yeast is added to a dough, the Yeast uses the sugars in the dough for respiration. By leaving the dough in a warm place for a short time (this is known as "proving" the dough) the Carbon Dioxide released by the Yeast causes the dough to double in size. It is this release of Carbon Dioxide that causes the bread to rise.

The diagram below shows the step by step process to make a loaf of bread:-


As a Baker, you would make baked goods for customers in shops and supermarkets. Or you’d bake and sell your hand-made products in a small craft bakery or delicatessen.

You could also experiment with ingredients and recipes to create new products for customers to enjoy. You’d need to meet hygiene, and health and safety standards.

You’d usually work in one of three types of bakery.

At a plant bakery, you’d use specialist machinery to make large amounts of baked goods for shops, supermarkets and other large customers.

As an in-store baker in a supermarket, you’d use some machinery to make fresh products to be sold in the store.

At a craft bakery, you’d make small quantities of products which will be sold in a shop, delicatessen or chain of specialist shops. The work would be more varied and although you’d use some machinery, you’d do much of the work by hand.


Baker Training

A Career as a Baker

Salary: from £21,000 to £42,000 per year

Distiller working hours: 39 hours a week over five days, with very early starts. Plant bakeries usually operate shifts on a rota system, which include nights and weekends. As an in-store or craft baker you would also be expected to cover weekends.

Typical entry requirements: Direct entry with qualifications at SCQF levels 4 to 6 or through a Modern Apprenticeship leading to relevant work-based experience and qualifications such as a Scottish Vocational Qualification in Food Manufacture: Craft Bakery Skills (SVQ level 2) or by completing a college course in an appropriate subject such as a NC Bakery (SCQF level 5) or NPA Bakery (SCQF level 4) .

Skills required:

  • Cooperating

  • Creative

  • Innovative

  • Attention to detail

  • Developing a plan

  • Managing resources

  • Time management

Alcohol Making

Yeast is essential in making alcoholic drinks. When Yeast is added to a sugary solution, the Yeast uses the sugars in the liquid for respiration, in a process known as Fermentation.

This respiration releases Ethanol as a waste product, making the liquid alcoholic.

The video below shows the step by step process of using Yeast to make Whisky:-


The fermentation process (using Yeast to convert sugar into alcohol) can be demonstrated in the school lab.

The method below shows how to convert the sugars in ribena into alcohol:-

Distillery Operator & Manager

You would oversee the production of spirits like whisky and gin that would then be bottled and sold – sometimes across the world.

As a distillery manager you’ll have one of the most senior positions at a distillery. You’re responsible for both the production of the spirit and the warehousing operations – where the spirit is stored.

You need to ensure that the distillery meets the agreed production targets (LOA – litres of alcohol) on an annual basis.

You’ll spend a lot of time looking for new ways to improve how the spirit is produced and the quality of the spirit.The duties of a distillery manager can vary depending on the size of the distillery. You will be more hands-on when working at a smaller distillery. A larger distillery might involve more delegation of tasks.


Distillery Operator

A Career as a Distillery Operator & Manager

Salary: from £25,000 to £60,000 per year

Distiller working hours: These vary by distillery from 35 to 38 hours per week. You'd normally work Monday to Friday, but may need to work extra hours on occasion and could be on-call. You’ll normally work in an isolated rural location. The working day is split between office duties and plant and warehouse duties as required.

Typical entry requirements: This job requires understanding of spirit production and management experience so you'll either need significant industry experience or a higher education qualification. This could be a degree (SCQF level 9/10) or postgraduate qualification (SCQF level 11/12) in spirit production or other relevant subjects, such as excise or quality control, plus industry experience.

There is an International Centre for Brewing and Distilling at Heriot-Watt University which offers a degree course in brewing and distilling.

Skills required:

  • Cooperating

  • Verbal communication

  • Problem solving

  • Attention to detail

  • Developing a plan

  • Managing resources

  • Delegating

  • Making decisions

  • Taking responsibility

  • Understanding