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YOUTUBE-parasporal crystals


It produces a crystalline protein body pathogenic for the larvae of Lepidoptera.
It is used as a biological insecticide.











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crystalline body / parabasale crystals



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Bacillus thuringiensis

  • General information


    • Bacillus thuringiensis is distinguished by its characteristic parasporal crystals

      Taxonomy
      Family: Bacillaceae
      Bacillus cereus group: B. anthracis, B. cereus, B. mycoides, B. thuringiensis

      Natural habitats
      Endospores are widespread in soil and many other environments.
      The organism had been isolated from all continents, including Antartica.

      Used as bio pesticide

      Clinical significance
      Bacillus thuringiensis is primarily known for its use as a biopesticide due to its production of insecticidal proteins (Cry toxins).
      While it is       not typically pathogenic to humans, it can cause rare infections in immunocompromised individuals, such as:
      - Wound infections      : In individuals with weakened immune systems.
      - Bacteremia      : Very rarely reported in clinical settings.
      B. thuringiensis is more clinically significant as a biocontrol agent in agriculture rather than as a human pathogen. Its antibiotic susceptibility and potential for causing infections are minimal in healthy individuals.

  • Gram stain

    • Large Gram positive (variable) rods,

      1.1-1.2 x 3.0-6.0 µm
      (only B.cereus + B.megaterium group >1 µm)

      The bacilli tend to occur in chains

      Spore shape: ellipsoidal
      Spore position: central, paracentral or subterminal
      Sporangium swollen: negative

      Spores may lie obliquely in the sporangia

      Parasporal bodies within the sporangia.
      These crystalline protein inclusions may be bipyramidal, cuboid, spherical to ovoid, flat rectangular or heteromorphic in shape.

      They are formed outside the exosporium and readily separate from the liberated spore.

      They are known as delta-endotoxins or insecticidal crystal proteins.

      The bacilli tend to occur in chains

      Capsule not present

  • Culture characteristics

    • Facultative anaerobic

      BA: they are usually whitish to cream in color, large 2-7 mm, and vary in shape from circular to irregular with entire to undulate, crenate or fimbriate edges and they usually have matt or granular textures.

      Sometimes smooth and moist colonies may appear.

      Hemolytic

      BBAØ: growth

  • Characteristics

  • References

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