Facts about Bacteria and Viruses

Bacteria and viruses are often confused with each other, but they are very different. Bacteria are usually harmless and viruses are usually harmful, though there are bad bacteria and useful viruses.

Bacterial Facts

• Bacteria (singular ‘bacterium’) are made up of only one simple cell – they are called single-celled organisms.

• A bacterium can be shaped like a sphere (coccus), rod (bacillus) or spiral (spirillum).

• Bacteria are about 1000 nanometres in size (a nanometre is one millionth of a millimetre).

• Different bacteria can live at a huge range of temperatures, from ice to hot springs, and can even live in radioactive waste.

• People have more bacterial cells in their bodies than human cells – and more than there are people on the planet.

• Most bacteria are useful – gut bacteria produce vitamins and help people (and animals) digest their food, and bacteria in the roots help legumes (plants in the pea and bean family) get nitrogen out of the soil, which helps them to grow.

• Bacteria are used in making cheese, yoghurt and sourdough bread.

• Bacteria produce oxygen – perhaps as much as half of the oxygen in the atmosphere.

• Bacteria (usually dead or weak ones) are used to make vaccines. 

Viral Facts

• Viruses are simpler than bacteria, made up of genetic code (DNA or RNA) with a protein shell – some scientists do not describe them as being alive.

• Viruses are 20 to 250 nanometres in size.

• Viruses can’t reproduce (make new viruses) on their own – they need to take over another cell (plant, animal or human).

• Some viruses are useful – viruses called bacteriophages (means ‘bacteria eater’) kill bacteria and are used to protect people against harmful bacteria in food.

• Most viruses cause disease – colds and flu are caused by viruses, as well as common diseases like chickenpox, measles, mumps and German measles (rubella). HIV, which causes AIDS, is a virus.

• Once people have had some viral infections, like chickenpox, it makes them immune from having it again.

Know more about bacteria and viruses.