The World of Bacteria

Bacteria are the oldest known organisms on Earth.  Fossils indicate that bacteria have inhabited the planet for nearly 3.5 billion years.  Over this time bacteria have evolved into unicellular organisms capable of existing in the most extreme and diverse conditions.  Bacteria are found on the tops of mountains and in the bottom of oceans, however, they are most commonly found in our natural environment. Bacteria are described as unicellular prokaryote organisms because they do not  possess membrane bound organelles.  Instead of having a membrane bound nucleus bacteria have a nucleoid, a region where bacterial DNA is localized. Bacteria have many different morphologies.  Cocci are spherical bacteria that can exist singly, in pairs (diphlococci), in chains (streptococci), or in clusters (staphylococci).  Bacteria also exist as rod shaped structures known as bacillus or helical structures known as spirilla. Bacteria are commonly classified on the basis of their cell wall structure using a technique called the gram stain.  The gram stain uses a violet and iodine dye to stain bacteria. Bacteria with a plasma membrane and cell wall appear purple, whereas bacteria with an outermembrane, cell wall, and plasma membrane appear red.

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The Antibiotic Crisis Tutorial

Learn More About:

   Gram Positive Bacteria

   Gram Negative Bacteria

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