study about virus

1. Welcome to our
Presentation

2. Jashore University Of Science And Technology
Department of Pharmacy
Course Title: Pharmaceutical Microbiology-ll
Course Code : PHAR -1211
A Presentation on "Virus"
Presented by- Presented to-
181003,181004,181005,181008 Dr. Md. Obayed Raihan
Associate Professor
Jashore University Of
Science &Technology

3. Outlines
Introduction to virus
History of virus
Characteristics of virus
Morphology of virus
Classification virus
Replication of virus
Cultivation of virus
Importance of virus

4. Introduction to Virus
▪ Virus is an ultra-microscopic infective agent that
consists of a nucleic acid and protein coat.
▪ The word virus was derived from a latin word, which
means 'toxic.'
▪ The study of virus is called 'virology .' It is W.M.
Stanly who is considered as the Father of virology.

5. History of Virus
• In 1892,Russian Scientist Dimitri Ivanovosky
showed that tobacco mosaic disease was caused
by an agent smaller than Bacteria
• In 1898, Dutch scientist Beijerinck realised that
the agent was different from bacteria and termed
as 'Virus'
• In 1935, W.M. Stanely first crystallized Virus from
tobacco leaves

6. Characteristics of virus
• They are acellular, obligate parasites.
• They are composed of nucleic acid
(DNA/RNA)and protein coat called 'capsid.'
• They are very small in size, usually 12 to 300 nm.
• They do not respire, do not metabolize, do not
grow but they do reproduce.
• They cannot grow and multiply without a host
living cell.

7. Morphology of virus
☆ Size of Virus :
• Virus is too small that it can't be seen in naked
eye ; even not precisely shown by light microscopy
• They can be seen by using electrical microscopy.
• Virus display a wide range of sizes. Most virus
have size ranging between 12 to 300 nm
• The smallest virus is Footh and Mouth virus(8nm)
and the biggest virus is Vaccinia virus (300nm)

9. ☆ Shape of Virus :
Virus may be categorised into following
morphological shapes:
• Helical virus : They have a halical structure that
resembles long rod structure.
• Polyhedral virus : They are many sided. Like
rectangular,triangular or tetrahedral shaped.
• Enveloped virus : Their capsid is covered by an
envelope.
• Complex virus : They have a complicated structure.

11. ☆ Structure of virus :
Most virus composed of 2 main structure :
a) Protein coat : Virus sorrounded by a protein
coat,called 'Capsid.' Sometimes the capsid is
composed by many sub-units, called 'Capsomeares.'
b) Nucleic acid : Viruses contain Nucleic acid, either
DNA or RNA ; but never have the both.

12. Classification of Virus
☆ Based on Size and Shape : 6 types-
i. Oval shaped : Influenza virus
ii. Spherical : Polio virus,TIV, HIV
iii. Rod-shaped : TMV, Mosaic virus
iv. Cubical : Herpes,vaccinia
v. Cylindrical : Ebola virus
vi. Tadpole : T2,T4,T6 bacteriophage

14. ☆ Based on Nucleic Acid : 2 types-
i) DNA virus : It has DNA as its genetic material.
Example- TIV,Vaccinia virus,herpes virus.
Mostly the DNA is double-stranded, but some viruses
have single stranded DNA like M13 colifuz.
ii) RNA virus : It has RNA as its genetic material .
Example- TMV,HIV,Polio virus.
Mostly the RNA is single-stranded, but some viruses
have Double-stranded RNA like Reo virus.

15. ☆ Based on host range :
i) Plant virus : viruses that infect plants.
Example: TMV, Alpha mosaic virus.
ii) Animal virus : viruses that infect animals.
Example: HIV, Flavi virus.
iii) Bacteriophage : viruses that infect bacteria.
Example: T2,T4,T6 bacteriophages
iv) Cyanophage : viruses that infect cyanobacteria.
Example: LPP1,LPP2

16. Replication of Virus
• Virus are intracellular obligate parasites which
means they can't replicate without a host cell.
• A virus itself is inert,it lacks needed components
that a cell have to reproduce.
• When a virus infects a cell, it marshals the cells
ribosome, enzymes & much of the cellular
machinery to replicate.

17. The viral replication is characterised by the following
steps :
i) Attachment : First, the virus attacks the receptor site
on the host's cell.
ii) Penetration : The virus attacks and penetrates the
cell wall and plasma membrane. Then the virus injects
its genetic material into the host's cell.
iii) Replication : The viral DNA takes over the host cell's
metabolism,causing the DNA transcripted into mRNA
and that are translated into proteins.

18. iv) Assembling : After many copies of viral
components are made from proteins,they are
assembled into complete viruses spontaneously.
v) Release : The new viruses lysis the host cell wall,
then release and continue infect other cells.

19. Here is a diagram of viral replication process-

20. Cultivation of virus
• Viruses are obligate intracellular parasites .So they
depend on host for their survival.
• They cannot be grown in non-living culture media or
on agar plates alone, they must require living cells to
support their cultivation.
• The two useful methods for cultivation of viruses are
:
i) Cell culture
ii) Embrayonated eggs method

21. ☆Cell Culture:
In this method Bacteriophages can be grown in
bacterial culture on solid media.
• A bacteriophage sample is mixed with host bacteria
and malted agar .The agar containing the
bacteriophages and host Bacteria is then poured into a
agar growth medium.
• The virus- bacteria mixture solidifies into a thin top
layer,where each virus infects a bacterium,multiplies
and releases several hundred new viruses.

22. ☆ Embrayonated eggs method :
The embrayonated eggs is the most convenient and
inexpensive methods.
• First, a hole is drilled in the shell of embryonated
eggs.
• Later a viral suspension is injected into the eggs.
• There are several membranes in the egg and the
virus is injected near the most one appropriate for
its growth.

23. • The viral growth is signal by the death of embryo or
by formation of pocks on the egg membrane.

24. Importance of Viruses
• In Biological Studies : Viruses have been used in
genetic Research and understanding of the genes,
DNA replication ,transcription and translation.
• In Medicine : Viruses are being used as vectors
that can target,infect and destroy host cells of
pathogens.
• In Nanotechnology : Viruses are used as carriers
for genetically modified sequence of genomes to
the host cell.

25. • In Agriculture : Viruses are used to make
productive transgenic plants that are preventive of
pathogens and defective microorganisms.

26. References
• www.wikipedia.org
• www.britannia.com
• www.microbiologyonline.org
• www.sciencedirect.com

27. Do you have any Questions?