Microorganisms

Types of Microorganisms:

1. Bacteria
2. Fungi
3. Viruses

1. Bacteria

• Single celled
• Asexual reproduction (very quickly).
• Most are harmless to humans.
• Beneficial bacteria: antibiotics, production of yoghurt and cheese.
• Harmful bacteria: food spoilage, illness (sore throat).

2. Fungi

• Some are single celled e.g yeast
• Some are multi celled e.g mushrooms
• No chloroplasts-they cannot make their own food.
• Useful fungi: yeast, used in the baking and brewing industry.
• Harmful fungi: cause disease e.g. ringworm.

3. Viruses

• Do not reproduce-they replicate.
• Antibiotics cannot kill viruses.
• Viruses cause diseases such as chickenpox, measles and AIDS.

Actions of Microorganisms

Beneficial Actions	Harmful Actions
Decompose organic waste	Causes diseases
Used in making cheese, yogurt and in brewing beer.	Spoil food by causing rot
Produce antibiotics	Damage crops

Preserving Food

Although it's tough to completely prevent food from spoilage because of microbes, we can slow down their effects.

Preservation Method	How it Works
Freezing	No water available for microorganisms to survive.
Pasteurisation	Milk is heated to a high temperature to kill microorganisms .
Refrigeration	Temperature is too low for most microorganisms .
Salting	Salt removes water from microorganisms, so they die.
Drying	Removes water, making it hard for microorganisms to grow.