Viruses
This presentation is the property of its rightful owner.
Sponsored Links
1 / 34

Viruses PowerPoint PPT Presentation


  • 95 Views
  • Uploaded on
  • Presentation posted in: General

Viruses. Alive?. They are reproduce Carry on the metabolism Organize the cell They contain enzymes, nucleic acids, carbohydrates, lipids Adapt to changing environments. How about virus?. They are reproduce, has macromolecules, adapt to changing environment  alive

Download Presentation

Viruses

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Viruses

Viruses


Alive

Alive?

  • They are reproduce

  • Carry on the metabolism

  • Organize the cell

  • They contain enzymes, nucleic acids, carbohydrates, lipids

  • Adapt to changing environments


How about virus

How about virus?

  • They are reproduce, has macromolecules, adapt to changing environment  alive

  • They are not cells, lack any significant metabolism  not alive


Viruses

  • Host range: spectrum of organism can be attacked by virus

  • Animal virus, plant virus, bacterial virus (bacteriophages/phages)

  • Only attack single species  depend on receptor (proteins)


Viruses

20 nm - 300 nm

(1/3-1/10 bacteria)

Size

No ribosom, cytoplasm, nucleus

Nucleic acid wrapped by protein coat

Largest:77 genes – T4(1/50 x E.coli),

Smallest: 3 genes


Viral structure

Viral Structure


Capsids

Capsids

  • Composed of protein subunits called capsomeres.

  • Functions

    • Protective

    • Recognition/attachment to host cells

    • Introduction of nucleic acid into host cell


Envelopes

Envelopes

  • Composition

    • Lipids from host cell membrane

    • Proteins

    • Glycoproteins

  • Function

    • Recognition/attachment to host cell


Genome

Genome

  • RNA or DNA

  • Double or single-stranded

  • Segmented or nonsegmented

ds DNA

ss DNA

ss RNA nonsegmented

ds RNA segmented


Viral shape

Viral Shape

Helical

Isometric (cubic)


Viral shape1

Complex

Viral Shape


Classification of viruses

Classification of Viruses

  • Host range

    • Very specific

  • Enveloped or nonenveloped

  • Type of nucleic acid

  • Shape


Bacteriophage

Bacteriophage

  • Viruses that infect bacteria.


Types of bacteriophage

Types of Bacteriophage

  • Virulent

    • Lytic multiplication cycle

  • Temperate

    • Lysogenic multiplication cycle


Viruses

E. coli host bacillus

Bacteriophage

Adsorption

Lytic Cycle


Viruses

E. coli host bacillus

Bacteriophage

Bacterial

DNA

Viral

DNA

Lytic Cycle

Adsorption

Penetration


Viruses

E. coli host bacillus

Bacteriophage

Bacterial

DNA

Viral

DNA

Lytic Cycle

Adsorption

Penetration

Lytic

phase

Duplication of phage components;

replication of virus

genetic material


Viruses

E. coli host bacillus

Bacteriophage

Bacterial

DNA

Viral

DNA

Lytic Cycle

Adsorption

Penetration

Lytic

phase

Eclipse phase

Duplication of phage components;

replication of virus

genetic material

Assembly of

new virions


Viruses

E. coli host bacillus

Bacteriophage

Bacterial

DNA

Viral

DNA

Lytic Cycle

Adsorption

Penetration

Lytic

phase

Eclipse phase

Duplication of phage components;

replication of virus

genetic material

Maturation

Assembly of

new virions


Viruses

E. coli host bacillus

Bacteriophage

Bacterial

DNA

Viral

DNA

Lytic Cycle

Release of viruses

Adsorption

Virion phase

Lysis of weakened cell

Penetration

Lytic

phase

Eclipse phase

Duplication of phage components;

replication of virus

genetic material

Maturation

Assembly of

new virions


Lysis

Lysis

Burst size

http://www.oranim.ac.il/courses/microbiology/phagelab.htm


Viruses

Lysogenic Cycle

lysogen


Lysogenic state

Lysogenic State

Prophage


Phage life cycle choices

Phage Life Cycle Choices


Lysogenic conversion

Lysogenic Conversion


Propagation of bacteriophage

Propagation of Bacteriophage

Mix with molten soft agar

Infect bacteria

Plate

plaque


Determining titer

Determining  Titer

http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap9.html


Viruses

Seven steps in Generalised Transduction

1. A lytic bacteriophage adsorbs to a susceptible bacterium.

2. The bacteriophage genome enters the bacterium. The genome directs the bacterium's metabolic machinery to manufacture bacteriophage components and enzymes

3. Occasionally, a bacteriophage head or capsid assembles around a fragment of donor bacterium's nucleoid or around a plasmid instead of a phage genome by mistake.


Viruses

Seven steps in Generalised Transduction (cont’d)

4. The bacteriophages are released.

5. The bacteriophage carrying the donor bacterium's DNA adsorbs to a recipient bacterium


Viruses

Seven steps in Generalised Transduction (contd)

6. The bacteriophage inserts the donor bacterium's DNA it is carrying into the recipient bacterium .

7. The donor bacterium's DNA is exchanged for some of the recipient's DNA.

http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/genetics/recombination/transduction/transduction.html


Viruses

Six steps in Specialised Transduction

1. A temperate bacteriophage adsorbs to a susceptible bacterium and injects its genome .

2. The bacteriophage inserts its genome into the bacterium's nucleoid to become a prophage.


Viruses

Six steps in Specialised Transduction (cont’d)

3. Occasionally during spontaneous induction, a small piece of the donor bacterium's DNA is picked up as part of the phage's genome in place of some of the phage DNA which remains in the bacterium's nucleoid.

4. As the bacteriophage replicates, the segment of bacterial DNA replicates as part of the phage's genome. Every phage now carries that segment of bacterial DNA.


Viruses

Six steps in Specialised Transduction (cont’d)

5. The bacteriophage adsorbs to a recipient bacterium and injects its genome.

6. The bacteriophage genome carrying the donor bacterial DNA inserts into the recipient bacterium's nucleoid.

http://www.cat.cc.md.us/courses/bio141/lecguide/unit4/genetics/recombination/transduction/spectran.html


  • Login