What are microorganisms, and how do we use them in food and biotechnology?
The main types of microorganism (bacteria, viruses and fungi), the conditions microorganisms need to grow, their useful roles in food production such as yoghurt and bread, and the use of microorganisms in biotechnology including aseptic technique.
A focused CCEA GCSE Biology answer on microorganisms, covering bacteria, viruses and fungi, the conditions they need to grow, their useful roles in food production, biotechnology, and aseptic technique.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
CCEA wants you to name the main types of microorganism, describe the conditions they need to grow, describe their useful roles in food production and biotechnology, and explain aseptic technique.
Types of microorganism
Conditions for growth
Microorganisms grow fastest with warmth (a suitable temperature), moisture (water), a supply of food (nutrients), and often oxygen (though some grow without it). Removing these conditions, for example by drying, cooling or salting food, slows their growth, which is how food is preserved.
Useful roles in food production
Biotechnology and aseptic technique
In biotechnology, microorganisms are grown in large vessels (fermenters) to make foods, medicines (such as antibiotics and insulin) and other products. When culturing microorganisms, aseptic technique is used to prevent contamination by unwanted microorganisms: equipment is sterilised, bottle necks are flamed, and work is done near a flame.
Examples in context
Example 1. Why salting and drying preserve food. Microorganisms that spoil food need water and nutrients to grow. Salting food draws water out by osmosis, and drying removes water directly, so the microorganisms cannot grow and the food keeps for longer. Cooling in a fridge slows their growth, and freezing almost stops it. These traditional and modern preservation methods all work by removing one of the conditions microorganisms need, which is a neat application of how microorganisms grow.
Example 2. Yoghurt and the drop in pH. When bacteria are added to warm milk, they ferment the milk sugar (lactose) into lactic acid. The acid lowers the pH of the milk, which causes the milk proteins to clump together and thicken, and gives yoghurt its sharp, sour taste. The same drop in pH also makes the conditions less suitable for spoilage microorganisms, helping the yoghurt keep. This links the useful role of bacteria to both the texture and the preservation of the food, a common CCEA biotechnology context.
Try this
Q1. Name the gas that makes bread dough rise. [1 mark]
- Cue. Carbon dioxide.
Q2. Why is aseptic technique used when culturing microorganisms? [1 mark]
- Cue. To prevent contamination by unwanted (possibly harmful) microorganisms.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA 20204 marksDescribe how yoghurt is made using microorganisms.Show worked answer →
Four marks for the organism, the conditions and the chemistry.
Milk is first heated (pasteurised) to kill any unwanted microorganisms, then cooled.
A culture of bacteria (for example Lactobacillus) is added.
The mixture is kept warm so the bacteria respire and ferment the lactose (milk sugar), producing lactic acid.
The lactic acid lowers the pH, which thickens the milk and gives yoghurt its sour taste.
Markers reward heating the milk, adding the bacteria, warm conditions, and lactic acid produced from lactose, thickening the milk.
CCEA 20193 marksExplain why aseptic technique is used when culturing microorganisms.Show worked answer →
Three marks for the purpose and a method.
Aseptic technique keeps the culture free from unwanted microorganisms (contamination).
It stops harmful microorganisms from the air or surroundings getting into the culture, which could make people ill or spoil the results.
Methods include sterilising equipment, flaming the neck of bottles, and working near a flame.
Markers reward preventing contamination, avoiding the growth of harmful microorganisms, and at least one correct aseptic method.
Related dot points
- Pathogens as disease-causing microorganisms and how they spread, the body's first-line defences such as the skin, and the role of white blood cells in defending the body by phagocytosis and antibody production.
A focused CCEA GCSE Biology answer on defence against disease, covering pathogens and how they spread, the body's first-line defences such as the skin, and the role of white blood cells in phagocytosis and antibody production.
- How the immune system produces memory cells for long-term immunity, how a vaccine uses a dead or weakened pathogen to make the body immune, and how vaccination protects individuals and populations (herd immunity).
A focused CCEA GCSE Biology answer on immunity and vaccination, covering memory cells and long-term immunity, how a vaccine uses a dead or weakened pathogen to make the body immune, and how vaccination protects individuals and populations.
- How antibiotics treat bacterial infections but not viral ones, the problem of antibiotic resistance and how to reduce it, the difference between medical and recreational drugs, and the effects of alcohol and tobacco on health.
A focused CCEA GCSE Biology answer on medicines and drugs, covering how antibiotics treat bacteria but not viruses, antibiotic resistance and how to reduce it, medical versus recreational drugs, and the effects of alcohol and tobacco.
- How genetic engineering transfers a gene from one organism to another using enzymes and vectors, examples such as insulin-producing bacteria and GM crops, methods of cloning, and the benefits and ethical issues.
A focused CCEA GCSE Biology answer on genetic engineering and cloning, covering how a gene is transferred between organisms, examples such as insulin and GM crops, methods of cloning, and the benefits and ethical issues.
- The carbon cycle including photosynthesis, respiration, combustion and decomposition, and the nitrogen cycle including the roles of decomposers and nitrogen-fixing, nitrifying and denitrifying bacteria.
A focused CCEA GCSE Biology answer on nutrient cycles, covering the carbon cycle through photosynthesis, respiration, combustion and decomposition, and the nitrogen cycle including the roles of the different bacteria.
Sources & how we know this
- CCEA GCSE Biology specification — CCEA (2017)