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Meet Your Favorite Bacteria

written by: Nick Oza•edited by: dianahardin•updated: 2/28/2015

Bacteria are some of the earliest organisms to have originated on Earth. There are countless numbers of bacteria. Some are good for humans, and others cause disease. Find out which are helpful and which are harmful.

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    Examples of Common Bacteria

    Bacteria Photomicrograph 

    Bacteria are microorganisms and can be either aerobic or anaerobic. They have no membrane-bound organelles and can adapt to their environment very quickly. They are found on all continents of the Earth, including Antarctica, and they can be found in some of the most extreme conditions on Earth, such as in hot water springs and near hydrothermal vents deep below the oceans.

    Bacteria exist in all species, from plants and animals to humans. Although the vast majority of bacteria are harmless to humans, some do cause serious infections and diseases. Below are some of the names of common bacteria, including their shape and function.

    1. Staphylococcus aureus - Staphylococcus aureus is a Gram-positive coccus (rounded shape) that is anaerobic. Staphylococcus aureus is also known as the "golden cluster seed," "golden staph" and "the seed gold". Staphylococcus bacteria are present in the nasal passages of humans and can be found on the skin and hair. If the bacteria contaminate food products and enter the digestive system, though, they can cause food poisoning. These bacteria are well known for causing what are known as staph infections. Staph infections can range from minor skin infections, such as pimples, folliculitis and scalded-skin syndrome, to serious infections, such as meningitis and toxic shock syndrome.

    2. Listeria monocytogenes - Listeria monocytogenes is a Gram-positive rod-shaped bacterium. It is anaerobic. The most common infection that these bacteria cause is Listeriosis. Symptoms of this infection are headaches, nausea and vomiting; however, if the infection spreads to the nervous system, it can cause meningitis. The Listeria monocytogenes bacterium also causes encephalitis, intrauterine infections, and meningitis, though this infection is usually restricted to newborn children and infants. These bacteria are extremely virulent, and 20-30 percent of infections result in death. Listeria is found in the soil, as well as in water. It can contaminate food sources. Items that are packaged can also be contaminated by Listeria.

    3. Vibrio - Vibrio is a genus of Gram-negative bacteria that are rod-shaped. The are found in saltwater sources and several species of vibrio are pathogens. Consuming food that is contaminated by Vibrio can result in diarrhea, vomiting and abdominal cramping. Vibrio can also cause serious life-threatening infections with those having a compromised immune system. Strains of Vibrio are known to cause gastroenteritis and septicemia, and Vibrio cholerae is known to cause cholera in humans.

    4. Clostridium botulinum - Clostridium botulinum is a Gram-positive bacterium that is rod-shaped and generally found in soil. These bacteria produce neurotoxins that cause botulism. Botulism is characterized by blurred vision, slurred speech, difficulty swallowing, muscle weakness and dry mouth. In infants, the symptoms can also be lethargy and constipation. Without treatment, botulism can lead to paralysis of the arms, legs and respiratory muscles.

    5. Escherichia coli (E.coli) - E.coli is Gram-negative, rod-shaped bacterium commonly found in the intestines of humans. Some strains, however, can cause food poisoning in humans, leading to bloody diarrhea and, in certain cases, kidney failure. The majority of E. coli infections are found to be associated with eating undercooked beef.

    6. Streptococcus - Strptococcus is a genus of Gram-positive bacteria that is spherical in shape. It is found in the mouth, skin, upper respiratory tract and intestines of humans. Most strains are harmless to humans. In the making of Swiss cheese, Streptococcus bacteria are a required ingredient for fermentation; however, certain strains of the bacteria can cause infections, such as meningitis, pneumonia, rheumatic fever, endocarditis and necrotizing fasciitis, otherwise known as flesh-eating bacteria.

    7. Lactobacillus acidophilus - Lactobacillus acidophilus is a species of the genus Lactobacillus. It is a rod-shaped bacterium commonly found in human intestines, the mouth and the female reproductive area. These bacteria convert sugars into lactic acid and have found great commercial use in dairy products. They are used in combination with other bacteria to produce acidophiles-type yogurt. They are also used in the treatment of bacterial vaginosis.

    8. Bifidobacterium animalis - Bifidobacterium animalis is a Gram-positive rod-shaped bacterium. It is anaerobic and found in the intestines of humans and other animals. This bacteria is well-known for improving the digestive system of humans and has been used in the treatment of patients with chronic constipation. A sub-species of Bifidobacterium animalis is used by the yogurt manufacturer Dannon, under the trade name "Bifidus Regularis."

    9. Lactococcus lactis - Lactococcus lactis is a Gram-positive rod-shaped bacterium capable of producing lactic acid, which has made it very important to the dairy industry. Nearly all forms of cheese, such as Brie, Cheddar, Parmesan and others, are produced with the use of strains of Lactococcus lactis, as is buttermilk.

    10. Lactobacillus reuteri - Lactobacillus reuteri is a Gram-positive rod-shaped bacterium found in the gut of humans. Certain strains of this bacterium are used in probiotics. It is sometimes referred to as a universal probiotic. It has also been used in the production of an antibiotic, through the fermentation of glycerol. Lactobacillus reuteri has proven useful in the treatment of diarrhea induced by rotavirus in children and for infant colic. It has been shown to kill Streptococcus mutants responsible for tooth decay; thus, it has been effective in promoting dental health.

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    Bacteria and the Ecosystem

    With new species being found each year, the list of bacteria keeps growing. Although they can cause infections in humans, these primitive ancestors of Earth also provide many benefits. They are an integral part of the Earth's ecosystem. Decomposition of carcasses would not be possible without bacteria, and several antibiotics on the market are made from strains of bacteria.With their ability to cause deadly infections and cure disease, we should both respect and admire bacteria.

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    References and Credits

    Staphylococcus Aureus by Jason Chavis on Bright Hub Science.

    More on Monocytogenes by Paul Arnold on Bright Hub Science.

    Streptococcal Infections from the National Institutes of Health, Medline Plus.

    Botulinum Toxin by Jason Chavis on Bright Hub Science

    Image Credits: Wikimedia Commons/MuntasirDu