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There are several types of bacteria. The majority of bacteria are made up of these types:

  1. Gram Positive Cocci-Include Streptococcus and Staphylococcus. Bacteria that fall into this group can cause harm to the human body but can perform useful functions as well.
  2. Gram Negative Cocci-Include Corynebacterium diptheriae which causes diphtheria.
  3. Gram Positive bacilli-Includes the bacteria Neisseria meningitidis which causes a form of meningitis.
  4. Gram Negative bacilli-Include bacteria such as E.coli, salmonella, and shigella.

Cocci have a spherical shape while bacilli have a rod shape.

There are 3 more types of bacteria which are less common. They are:

  1. Spirochaetes-This type is corkscrew shaped.
  2. Rickettsia-Only survives inside other cells. Causes typhus.
  3. Mycoplasma-Has no cell wall and can cause pneumonia.
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Bacteria are divided into three groups depending on their shape or morphology. Spherical bacteria are called cocci. Rod shaped bacteria are called bacilli and spiral bacteria are called spirochetes.

Cocci in clusters are called staphylococci, these cause "staph" infections. Cocci in chains are called streptococci. One type of these causes "strep throat". Bacteria in pairs are called diplococci, one type of which causes gonorrhea.

Some bacteria need oxygen to live. These are referred to as aerobic or aerobes. Other bacteria can live without oxygen, called anaerobic. Still others can live with or without oxygen and are called facultative.


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