1. Make your own balloon bacterium
Balloon Bugs
Make your own balloon bacterium

2. What are bacteria? Bacteria are living organisms.
They are so small you need a microscope to see them.
They come in different shapes and sizes.
They can be found everywhere!
Bacteria are a type of microbe. They are single celled organisms that can grow and divide rapidly in the right conditions.
Bacteria are microscopic and can only be seen using a microscope. They can be all sorts of shapes and sizes and can be found in pretty much any environment you can think of, including Antarctic sea ice and deep sea vents.

3. How big are bacteria?
Bacteria are tiny! Millions can fit on a single pin head.
Bacteria are microscopic. The largest bacteria are around 10 micrometres that is 10 millionths of a metre! Or one hundredth of a mm or one thousandth of a cm
This image offers a sense of scale by zooming in on bacteria found on the head of a pin.
A useful video that can be used to give an idea of the size of bacteria can be found at:
Images: Genome Research Limited

4. What shape are bacteria?
There are three main shapes of bacteria:
Balls
(Cocci)
e.g. Staphylococcus sp.
Rods
(Bacilli)
e.g. Citrobacter sp.
Spirals (Spirochetes)
e.g. Campylobacter sp.
Bacteria can be divided into groups by their shape. Cocci are shaped like spheres or balls, bacilli are shaped like rods and spirochetes are shaped like a spiral.
To help the students visualise this you can use food items such as sweets. For example, cocci can be represented using M&Ms or Maltesers, bacilli can be represented using Tic Tacs and spirochetes can be represented using Flump marshmallow (spiral shapes), if you can’t find Flumps you can use spiral pasta.
Images: Sharon Peacock, Oxford University; David Goulding, Wellcome Trust Sanger Institute; De Wood, Pooley, USDA, ARS, EMU

5. How do bacteria move?
Some bacteria have special structures that help them move. These are called flagella.
flagellum
flagella
Some bacteria can move around their environment using a special tail-like structure called a flagellum. Some bacteria , like Campylobacter have just one flagellum to help them move (see right image), others like Salmonella Typhimurium have several flagella to help them move around.
Images: David Goulding, Wellcome Trust Sanger Institute; De Wood, Pooley, USDA, ARS, EMU

6. Some bacteria can make us feel ill
Streptococcus pneumoniae
Causes a sore throat and pneumonia
Salmonella Typhimurium
Causes food poisoning
Campylobacter jejuni
Causes food
poisoning
Some bacteria are harmful and if they enter our bodies can cause disease. They can release poisons or toxins that make us feel ill.
The side shows three pathogenic (harmful) bacteria that can make humans ill. Streptococcus pneumoniae can cause a sore throat but if it spreads further into the lungs it can become a lot more serious and cause pneumonia.
Salmonella Typhimurium* can enter bodies through contaminated food. It causes food poisoning which leads to stomach pain, sickness and diarrhoea.
Campylobacter jejuni also causes food poisoning if it enters the body through contaminated food and leads to the symptoms of stomach pain, sickness and diarrhoea.
* Note on Nomenclature: This is a subspecies of the bacteria Salmonella enterica serovar Typhimurium so for simplicity the convention is to shorten it to Salmonella Typhimurium
Images: Rocky Mountain Laboratories, NIAID, NID; David Goulding, Wellcome Trust Sanger Institute; De Wood, Pooley, USDA, ARS, EMU

7. Are there “good” bacteria?
Not all bacteria are harmful. There are some bacteria that are used in producing cheese and yogurt. This is called Lactobacillus.
It is important to stress that not all bacteria are harmful. Some bacteria are found in food products, in particular dairy products such as yoghurt and cheese, and are thought to play a role in keeping us healthy.
The major type of bacteria found in dairy products is called Lactobacillus.
The term probiotic is used to describe some yogurts advertised on the TV. Probiotic means the product contains live microorganisms that “when administered in adequate amounts confer a health advantage to the host” (FAO/WHO 2001*). It is thought that that these bacteria can help us maintain a healthy digestive system and can also can help us to fight off infection.
*Report of a Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria (October 2001).
Images: Genome Research Limited

8. Can you make a balloon bacterium?
Choose from the three bacteria below
Streptococcus pneumoniae
Use this slide to introduce the activity and room set up.
Test the students and see if they can remember what illnesses the bacteria cause.
Salmonella Typhimurium
Campylobacter jejuni
Images: Rocky Mountain Laboratories, NIAID, NID; David Goulding, Wellcome Trust Sanger Institute; B Wren, London School of Hygiene and Tropical Medicine