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An Introduction to Helpful and Harmful Bacteria

written by: •edited by: Paul Arnold•updated: 10/14/2011

We have a deep and long-term relationship with bacteria as our bodies, inside and out are swarming with these tiny microscopic cells. Some are friends others are foes. Which are the good guys and which types would do us harm? Find out in this guide to the relationships between bacteria and humans.

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    Human Bacterial Flora

    Bacteria often get a bad rap, which is not too surprising as they are responsible for some of the deadliest diseases known to man. In addition there are those that have acquired resistance to many of the antibiotics that we throw at them. However, there are many types of bacteria that are useful to us and indeed are necessary for some of our bodily functions. For example, Lactobacillus acidopholus is a species that helps the digestive process, and many bacteria occupy places in the body that could otherwise be taken up by harmful strains. These are known as commensals and do us no real harm.

    Bookmark this guide to keep you primed on the positive and negative interactions between the bacterial world and humans.

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    Outnumbered by Alien Cells

    Here's a startling fact to kick off with. Most of the cells in your body are not your own. In fact it has been estimated that there are ten bacterial cells for every one human cell. So what does that make us? Some kind of bacteria-human hybrid? Well, yes according to some scientists.

    From the tips of your toes to the top of your head you are crawling with bacteria. They have you covered. They are on your skin, eyes, nose, inside your mouth and intestines and much more. Individual bacteria cannot be seen by the naked eye, but they often form colonies which can easily be spotted.

    Inside the body there a plenty of havens for microbial life to survive and thrive. In your gut alone there are anywhere between 500 and 1000 species of bacteria. But don't panic! Many of these populations have roles that are important for human physiology and under normal circumstances do not have any harmful effects.

    Mouth Bacteria: It's a Jungle in There

    The Bugs that Lurk on Your Hands

    Bacteria and the Roles they Play in the Human Body

    Your Skin is Teeming with Microbes

    Three Types of Helpful Bacteria

    Meet Some Bacterial Good Guys

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    Spotlight on Pathogens

    Of course our relationships with some types of bacteria are not always harmonious. Bacteria like Staphylococcus and Streptococcus that inhabit our skin are generally speaking harmless, but danger can lurk if they get into a wound or further into the respiratory tract. The principal routes that bacteria take into us are via cuts and scrapes, through the nose and mouth and by being on and in the food we eat.

    Disease-causing bacteria are pathogenic and come in many different forms that can cause a variety of conditions. Some infections create mild discomfort, others can be fatal.

    Although bacterial infections are common occurences many can be avoided by good hygiene practices such as hand-washing, good cleaning and good cooking.

    Getting to Grips with Staphylococcus Aureus

    A Brief History of Tuberculosis

    Three Diseases Caused by Bacteria

    Cholera: The Water of Death

    Infection by Shigella

    Probing the Bacteria that Causes Tetanus

    Insights into Anthrax Bacteria

    Putting Streptococcus Under the Spotlight

    Key Facts about Lyme Disease

    Flesh Eating Bacteria FAQ

    The Spread of the Black Death

    The Bacteria that Take a Shower with You

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    Bacterial Weapons at the Ready

    Those bacteria that are disease-causing have an arsenal of weapons, known as virulence factors that can make us ill. Most bacteria need to be inside our bodies or in close contact with them to cause us harm. These infections are wars between the host and the invading bacteria, with the former trying to make it as difficult as possible for the latter to take a hold.

    Examples of virulence factors include toxic compounds that cause a variety of effects such as vomiting, diarrhea, pain and paralysis, and hairlike structures known as pili that attach bacteria to sites of our body so they cannot be washed away.

    Bacteria can be wily foes. What makes some of them resistant to powerful antibiotics is that their virulence factors mutate and evolve, rendering our therapeutic weapons useless. It is because of this that scientists are constantly researching new antibiotic treatments.

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    Fighting Back

    But to those types of bacteria that are deadly agents of disease watch out! Science is coming up with news ways to defeat you. Many approaches are being tried and avenues explored, some involving genetic engineering, and others the use of bacteriophages (deadly viruses that infect and destroy bacteria). Phage therapy was used in the early parts of the twentieth century but fell out of favor when antibiotics appeared on the scene. However, it is enjoying something of a comeback since the rise of antibiotic resistance.

    How to Defeat Flesh Eating Bacteria

    Bacteriophages: A Bacterium's Worst Nightmare