<em>Salmonella enteritidis</em> b/w <em>Salmonella enteritidis</em>

Salmonella enteritidis

Salmonella enteritidis causes the illness known as food poisoning. Infection occurs when food, such as raw chicken, contaminated with the bacteria is eaten. The bacteria multiply inside the person's intestine, making toxins. Symptoms including vomiting, nausea, abdominal pain and diarrhoea. These usually start 8-48 hours after eating contaminated food.

Introducing microbes

Micro-organisms (or microbes for short) play a very important role in our lives. Some microbes cause disease but the majority are completely harmless. In fact we couldn’t live without them, but they could live without us.

These microscopic organisms play a key role in maintaining life on earth, fixing gases and breaking down dead plant and animal matter into simpler substances that are used at the beginning of the food chain. Biotechnologists can also exploit the activities of microbes to benefit humans, such as in the production of medicines, enzymes and food. They are also used to breakdown sewage and other toxic wastes into safe matter. This process is called bioremediation.

Microbes are very small living organisms, so small that most of them are invisible. The majority can only be seen with a microscope, which magnifies their image so we can see them. In fact microbes are so tiny you would find over a million in a teaspoon of soil. They make up more than 60 % of the Earth’s living matter and scientists estimate that 2-3 billion species share the planet with us.

Micro-organisms occur in an amazing variety of shapes and sizes and they are divided into one of 6 groups:

Helicobacter pylori bacterium


More than just pathogens - can be friend or foe.

T4 bacteriophage


Smallest of all the microbes but are they alive?

A Petri dish culture of the fungus Penicillium notatum growing on agar


More than just mushrooms.

Two ciliated protozoans


Microbes with a taste for poo and so much more.

Filaments of Spirogyra


Microbial powerhouses essential for life.

Methanosarcina mazei


First found existing on the edge of life.

Geobacter metallireducens

Find out more about this metal-eating microbe.

Bacillus thuringiensis

Discover how this bacterium can be used as a pesticide.