Bacteria range from the essential and useful, to the harmful.

Essential bacteria

Without the key functions of some bacteria, life on earth would be very different:

  • Some bacteria degrade organic compounds for energy, and without bacteria, the earth would have no soil in which to grow plants.
  • Bacteria living in the gut can help animals break down food. These so-called ‘good bacteria’ help maintain the conditions necessary for food digestion
  • Some bacteria live on the root nodules of certain plants, for example, peas, beans and clover, and are able to ‘fix’ atmospheric nitrogen into a form that can be absorbed by the plant as a fertiliser.

Nature of science

Scientists have observed bacteria using microscopes to identify them. But it is the living processes that bacteria use and the wastes they give off that can be used either for human benefit or that cause disease.

Scientists believe it was the chemical processes of early cyanobacteria, harnessing the energy from the sun, that released the oxygen that makes up our atmosphere. It took approximately 2 billion years for the bacteria to build up enough oxygen in the atmosphere to allow for the evolution of multi-cellular organisms.

Useful bacteria

Bacteria have long been used by humans to create food products such as cheese, yoghurt, pickles, soy sauce and vinegar. We are also able to use bacteria to break down our sewage and to clean up oil spills.

Many bacteria are very fast growing – under ideal conditions, Escherichia coli (E. Coli) are able to double their number in 20 minutes. This makes them very useful tools in molecular biology and biochemistry, as they can be manipulated much faster than more complex and slower growing organisms. We can manipulate bacteria to grow a protein of interest, for example, insulin, and then grow them in large vats to produce a large quantity of the desired protein.

Harmful bacteria

Only a small handful of known bacteria are capable of causing disease. These bacteria are termed pathogenic.

To cause disease, the bacteria must invade the cells of a living organism. Most bacteria will not invade another living organism, and many more bacteria are rendered harmless by our immune systems, while others, such as gut bacteria, are beneficial.

In many developing countries, poor hygiene, limited access to clean water and poor (or no) sewage treatment leads to huge numbers of deaths from bacterial infections such as those that cause dysentery.

The advent of antibiotics like penicillin has greatly reduced the number of deaths due to bacterial infections. However, increased use of antibiotics in many western countries has led to the adaptation of antibiotic-resistant bacteria, which can lead to outbreaks of so-called ‘super bugs’, such as Multi-Resistant Staphylococcus aureus (MRSA). Scientists now believe that humans require contact with bacteria at an early age in order to ‘educate’ our immune systems between good and bad bacteria. The scientists believe that western societies’ obsession with antibacterial products has increased our chances of developing immune-related conditions such as asthma, allergies and eczema.

    Published 9 November 2008