VIRUS, VIROIDS, VIRUSOIDES, VIRION, and PRIONS

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Virus:
  • These are submicroscopic and acellular organisms 
  • They are obligate intracellular parasites
  • They contain either DNA or RNA
Chemical Composition:
  • Nucleic acid -- (Central Core)
  • Protein coat (Capsomere)
Note: An infectious viral particle is called Virion.

Viroids:
  • Contain only low molecular weight RNA (Single stranded RNA) and not protein coat.
  • Cause Potato Spindle Tuber disease 

 Virusoides:
  • They are like viroids, but are located inside the protein coat of a true virus
  • Virusoid RNA can be either circular or linear
 Prions:
  • lack their own genetic material
  • they consist of specific protein macro molecule, which is known as Prion protein pr Prep
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What is the Difference Between Gram Positive and Gram Negative Bacteria?

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There are several difference between Gram positive and Gram bacteria:



Gram Positive Bacteria
Gram Negative Bacteria
Peptidoglycan layer (thick)
Peptodoglycan layer (thin)
Polysaccharides (thin)
Lipopolysaccharides (thick)
Teichoic Acid present
Absent
Ribitol present
Absent
Absent
Porins
Glycolipids
Phospholipids
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What is Gram Staining?

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Gram staining is a procedure used to distinguish Gram positive bacteria from Gram negative bacteria.

Steps:

  • In the beginning, both Gram positive and Gram negative bacteria look alike. So, they are unstained.
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  • Crystal violet is used in the next step, both Gram positive and Gram negative bacteria become violet in color.
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  • In the third step, Iodine is used to stain. Both look alike i.e., violet in color.
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  • Now, bleaching is done with the help of acetone. After bleaching, Gram positive bacteria look violet and Gram negative bacteria contain no color.
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  • In the last step, both are stained with Safranin -- Gram positive bacteria get purple color while Gram negative bacteria get red color.
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