Bacteria | Definition, Types & Classification

By | April 24, 2019

Bacteria Definition

Domain Bacteria examples:

There are three main domains, bacteria is one of them. Examples of this domain are given below in the diagram below:

Bacteria

Bacteria

Bacteria Characteristics

Bacteria Facts

  • They are basically single-celled organisms.
  • They did not have the Nucleus as the eukaryotic cells have.
  • Rather than this its DNA, which is double strand, and circular, present in Nucleoid.
  • The nucleoid is an irregularly shaped region that does not have a nuclear membrane.
  • They also have a cell membrane and a cell wall that is often made of peptidoglycan.
  • Many cells require a cell wall in order to survive.
  • They reproduce by the process of binary fission.
  • It is basically the splitting of the bacterial cell when it comes to a specific size.
  • By the binary fission two daughter cells are produced which have the exact same amount of DNA as parent cell has.
  • They exchange their genetic material between the cells by the process called Horizontal gene transfer.
  • Bacteria Classification

    They are basically classified into five major groups. This classification is done on the basis of its shape. The spherical shape is called Cocci, Rod shape is called bacilli, Spiral shape is called spirilla, comma shape is called vibrios.

    Bacteria Shapes

    They usually occur in three shapes coccus, spiral, and Bacillus.

    Bacteria

    Bacteria

    1. Cocci shape:

  • Cocci shape:

  • Cocci shape:

    These are ovoid or spherical in shape. They are found in the chain or in the isolated form. For example, Diplococci are cocci occurs in pairs, streptococci exist in chains, and staphylococci are present in clusters of manifold cocci. Tetrads are which have square arrangements of four cocci. Sarcinae eight cocci cubes.

    1. Spiral Shape:

  • Spiral Shape:

  • Spiral Shape:

    They are spiral-shaped. Spirillums are basically thick, threatening spirals. Spirochetes are also spirals which have thin and flexible texture. Vibrios are comma shape rods which have a little twist.

    1. Bacilli Shape:

  • Bacilli Shape:

  • Bacilli Shape:

    They are basically rod-shaped. They sometimes present in isolate form while occasionally arranged in a chain. Diplobacilli are basically two bacilli which are arranged adjacent to each other.

    Bacteria Structure: 

    Bacteria Structure: 

    Bacteria

    Bacteria

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    Types of Bacteria

    Types of Bacteria

    Broadly there are two main types:

    1. Gram-positive bacteria

    2. Gram-negative bacteria

  • Gram-positive bacteria

  • Gram-positive bacteria

    Gram-positive bacteria

  • Gram-negative bacteria

  • Gram-negative bacteria

    Gram-negative bacteria

    Bacteria

    Bacteria

     

    Examples of Bacteria

    1. Escherichia coli.

    1. Escherichia coli.
    1. Escherichia coli.

    Common species are Escherichia coli. Its shape is Bacillus. Commonly found animals intestine including humans. In the intestine, they produce vitamin B complex and vitamins K. E. coli usually utilize in the laboratory for the research purposes. They reproduce rapidly due to this they are extensively used for research purposes. They are usually harmless but some species of E. coli can cause diseases in humans. They usually cause gastrointestinal problems in humans.

    Bacteria

    Bacteria

    2. Lactobacillus acidophilus

    2. Lactobacillus acidophilus
    2. Lactobacillus acidophilus

    Lactobacillus acidophilus is bacillus shape which commonly finds in vagina and intestine of human beings. Being probiotic, it is present in yogurt and food produces by fermentation.

    Bacteria

    Bacteria

    3.Clostridium botulinum

    3.Clostridium botulinum
    3.Clostridium botulinum

    Clostridium botulinum causes special disease Botulism. C. botulinum bacteria generate the neurotoxin botulinum that causes botulism. Its symptoms include blurred vision, paralysis, nausea, muscles weakness and trouble to breathe.

    Bacteria

    Bacteria

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