Protocol to Differentiate Various Types of Bacteria

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Microbiologists develop methods to classify bacteria.

Microscopic life-forms may be helpful or harmful to humans. Accordingly, microbiologists who study these entities classify each one according to makeup and characteristics. One of the most common microscopic life-forms is bacteria. The shape, function and form distinguish different types of bacteria.

  1. Pathogens and Flora

    • Some germs and bacteria are harmful.
      Some germs and bacteria are harmful.

      One of the greatest threats of bacteria is infection. However, all bacteria does not harm the human body. Bacteria normally live inside human beings in particular locations. For example, types include skin flora, urogenital flora, intestinal flora, oral cavity and nasopharyngeal flora. Flora are bacteria that normally live on the surface and within the human body. These microorganisms often help the body by competing with harmful microorganisms for space. Microbiologists describe harmful types of bacteria (and other microorganisms) as pathogenic.

    Shape and Form

    • Bacteria are named according to shape.
      Bacteria are named according to shape.

      Microbiologists name bacteria according to appearance. Spherical or berry-shaped bacteria is called coccus; cocci is the plural form. Spirillum is the name for spiral-shaped bacteria; the plural form is spirilla. The name for rod-shaped bacteria is bacilli; bacillus is the plural form. These descriptions can be preceded by prefixes such as strepto--meaning chain, staphylo--meaning cluster or diplo--meaning two. More complex forms of bacteria are called filamentous, which have the appearance of "jellybeans in a straw," according to the University of Albany School of Public Health.

    Gram Negative and Gram Positive

    • Microbiologists stain bacteria for observation under the microscope.
      Microbiologists stain bacteria for observation under the microscope.

      Researchers also classify bacteria according to the ability to absorb dye. The dyeing process is called gram staining. Bacteria that absorb the gram-staining dye appear purple under the microscope and are called gram-positive. Bacteria that do not absorb the dye are gram negative. The gram-negative bacteria are counter-stained to appear red under the microscope. Counter-staining is necessary to make gram negative bacteria visible. Physicians prescribe antibiotics according to the results of gram staining, which helps them select the most effective antibiotic.

    Aerobic and Anaerobic

    • Some bacteria require oxygen for survival.
      Some bacteria require oxygen for survival.

      Some bacteria need oxygen to survive; these types of bacteria are called aerobes. Microbiologists classify bacteria that survive only without oxygen as anaerobes or strict anaerobes. Bacteria that can survive with or without oxygen are called facultative.

    Food and Energy

    • Bacteria need food and energy to grow.
      Bacteria need food and energy to grow.

      Microbiologists categorize bacteria according to food and energy sources. Bacteria that get food from other living things are heterotrophs. Bacteria that manufacture their own food (from carbon dioxide) are autotrophs. Additionally, those that use light for energy are phototrophs; those that use chemicals for energy are chemotrophs.

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