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  • 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.
    Rights: Public domain - U.S. Government

    Campylobacter bacteria

    Campylobacter bacteria have a distinct spiral form and are a common cause of diarrhoea and dysentery. People can become infected from food and water contaminated with faeces due to poor hygiene or sewage treatment. Campylobacter bacteria are found in most chicken meat and if chicken meat is not well cooked or raw meat and juices contaminate other food, they can cause food poisoning.

    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.

    Rights: Public domain - U.S. Government

    Escherichia coli bacteria

    Escherichia coli (E. coli) is a rod-shaped bacterium that lives in the gut of warm-blooded animals. It is a crucial tool in modern biotechnology and often used in molecular biology laboratories due to its ease of culture and rapid growth. Scientists use E. coli to work with DNA and proteins from other organisms. It is a normally harmless bacteria that lives in the lower intestine though some strains of this bacterium can cause infection of the intestine, urinary tract and other parts of the body.

    Harmful bacteria

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

    Rights: Public domain – U.S. Government

    Pseudomonas bacteria

    Pseudomonas bacteria have some natural resistance to antibiotics, which is made worse by some drug treatments. They are a common hospital-acquired infection and will infect wounds and the respiratory tract.

    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.

    What is an immune response?

    Dr Mattie Timmer describes immune response as any action that your body takes against invading objects or microorganisms.

    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 ‘superbugs’, such as methicillin-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.

    Related content

    Use these articles below to discover more resources related to bacteria:

    Learn more about the history of antibiotics and antimicrobial resistance with this article and timeline. Find out what you can do to reduce the risk. The context for learning provides ideas on how to incorporate this wicked problem into authentic cross-curricular learning.

    Citizen science

    The Infection Inspection citizen science project is using E. coli to help develop a faster test for antibiotic resistance. They need your observation skills to help identify bacteria that have been impacted by antibiotics.

      Published 9 November 2008 Referencing Hub articles
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