Viruses~~~ :)

~~**Welcome**~~ :)

.. to our Microbiology B blog on viruses.
This blog will be posts regarding what we've learnt during microbiology B, or more.
We hope to share with you all regarding if what we've learnt, so that everyone knowledge on viruses would increase!

Click:
~1st tab to study more on viruses- introduction
~2nd tab is on what we've learn in lecture
~3rd tab is to watch video

Thanks for reading =) ENJOY

Here are some pictures~~~

Members

♥Eileen Ng Hui Qi
♥Tang Xu Yun
♥Koh Jia Huan
♥Canice Tay

NYP SCL MB0804

Credits for this blogskin to:

Exclusive design of Little-Miss-Wendy

Favicon & Cursors from Portfolio @ Pink-Inc

Other materials are from X X X X X

● @ Friday, January 16, 2009 ●

Lecture 14!
Virus Host Interactions 3..

1) Viral assembly and exit:
-Depends on site of synthesis
-Sites of protein synthesis (golgi body, endoplasmic reticulum)
-Sites for assembly (nucleus, golgi body, endoplasmic reticulum)

2) Budding

3) Release
-cell lysis
-budding at plasma membrane
-Accumulation of particles in vesicles and release via exocytosis

Sites of Viral Entry into Host:

-Skin

-Conjunctiva
-Urogenital Tract
-Repiratory Tract

-Alimentary tract

Virus Spread:
-Systemic infection
-Haematogenous spread
-Neural Spread

Modes of transmission:
-Respiratory Secretions (Rhinovirus, influenza, measles)
=Through speaking, sneezing, coughing, breathing and singing.
=Further transimission by contaminated hands

-Saliva(cytomegalivirus, herpesvirus,mumps,retrovirus)
=Kissing

-Faeces(enteric and hepatic virus)

-Blood(Arbovirus, Bunyaviridae and filoviridae)

Virus Induced injury:
-CPE
=Altered shape
=detachment from substrate
=lysis
=membrane permeability
=inclusion bodies
=apoptosis

-Shutoff of cellular functions

-Immunopathological lesions
=Impairment of immune response due to infection of immune cells
=Enhancement of immune response causing harmorrhagic fever

References:
http://myweb.lsbu.ac.uk/dirt/museum/margaret/758-2631a-2640350.jpg

Virus

Knowledges

**~~Viruses!!~~**
• Not made of cells.
• Cannot reproduce on their own.
• Do not grow or undergo division
• Do not transform energy.
• Lack machinery for protein synthesis.
• Are so small that they can only be seen with an electron microscope.

What are viruses made of?
• Viruses are composed of nucleic acid, proteins, in some cases, lipids as well. Nucleic acid which can be either DNA or RNA encodes the genetic information that is necessary to make copies of the virus.
• The nucleic acid is surrounded by a protective protein coat called a capsid. Some viruses are also surrounded by an outer membranous called an envelope, made of lipid and protein.

Structure of viruses?

Viruses display a wide diversity of shapes and sizes, called morphologies. Viruses are about 100 times smaller than bacteria. Most viruses which have been studied have a diameter between 10 and 300 nanometres.Most viruses are too small to be seen under a light microscope so scanning and tramission electron microscope are used to visulualise virus particle.

1) Helical structure

Structure of tobacco mosaic virus: the viral RNA is coiled inside the helix formed by repeating protein sub-units

2) Icosahedral structure

Electron micrograph of icosahedral viruses(Adenovirus)

3) Enveloped structure

Viruses are dependent on the envelope for their infectivity.

4) Complex structure

Structure of a typical bacteriophage

Shape of viruses?
There are predominantly two kinds of shapes found amongst viruses: rods, or filaments, and spheres. The rod shape is due to the linear array of the nucleic acid and the protein subunits making up the capsid. The sphere shape is actually a 20-sided polygon.

Genetic Change

How antigenic shift, or reassortment, can result in novel and highly pathogenic strains of human influenza

Viral Replication

DNA Viruses
The genome replication of most DNA viruses takes place in the cell's nucleus. If the cell has the appropriate receptor on its surface, these viruses enter the cell by fusion with the cell membrane or by endocytosis. Most DNA viruses are entirely dependent on the host cell's DNA and RNA synthesising machinery, and RNA processing machinery. The viral genome must cross the cell's nuclear membrane to access this machinery.

RNA Viruses
RNA viruses are unique because their genetic information is encoded in RNA. Replication usually takes place in the cytoplasm. RNA viruses can be classified into about four groups depending on their modes of replication. The polarity (whether or not it can be used directly to make proteins) of the RNA largely determines the replicative mechanism, and whether the genetic material is single-stranded or double-stranded. RNA viruses use their own RNA replicase enzymes to create copies of their genomes.

Reverse transcribing Viruses
Reverse transcribing viruses replicate using reverse transcription, which form DNA from an RNA template. Reverse transcribing viruses containing RNA genomes use a DNA intermediate to replicate, whereas those containing DNA genomes use an RNA intermediate during genome replication.