This presentation provides an overview of viruses including: 1) It defines viruses as ultra-microscopic agents consisting of nucleic acid and protein that can only replicate inside host cells. 2) It discusses the history of virus discovery and key figures like Ivanovsky, Beijerinck, and Stanley. 3) It describes the typical characteristics of viruses like their acellular and obligate parasitic nature, composition of nucleic acid and protein capsids, small size, and inability to metabolize. 4) It covers virus morphology, classification based on shape, size, nucleic acid, and host range, and the multi-step process of viral replication within host cells. 5) It discusses common

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?