Microbiology unit 3
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- Srtart as RNA and then translates into DNA on the Hosts DNA and replicates.
- (ex. HIV)
Order of Classifying Viruses
- Nucleic Acid (DNA,RNA)
- Capsid Symmetry (Shape)
- Envelope (Naked, Envelope)
- Family (Adenovirdae,Herpesvirdae,poxvirdae, etc)
- Virus (adenovirus, HSVI.Vaccina Virus, Reovirus, etc)
- Genome Size (36-38,120-200, 130-280,etc)
Host Range Refers to?
(and 2 examples)
refers to the spectrum(number) of Hosts that a virus can infect.
Ex. Poliovirus only infect humans
- Rhabdoviruses (broad infectious range) and can
- infect humans and animals
Tissue Specificity refers to?
Refers to the types of Cells that viruses can infect.
Ex. Papillomaviruses effect the cervical cells
- Cytomegaloviruses effect many cell organs and have
- no specificity for specific tissue
Viral Hosts Range and Tissue Specificity is influenced by?
- Ability of the virus to attach to the Host cell (have the right receptors to stick to the host).
- Presence of proteins and enzymes for Viral replication.
- The ability of the Virus to Release from the Hosts cell.
viruses that only infect bacteria cells
Bacteriophage structural components?
- Tail Sheath
- Tail (protein only)
- Plate and Tail Fibers
retracts so that the Genome can move from the head into the hosts cell's cytoplasm.
carries the genetic information necessary for replication and new phage particles.
Plate and Tail Fibers
attach phage to specific receptor sites on the cell wall of a succeptable host bacterium.
Lytic Replication (virulent phages) Stages?
Lysogeny (temperate phage) Stages?
(has 2 xtra steps)
- Lysogenic conversion (xtra step)
- Induction(xtra step)
involves the chemical attraction and attachment of the virus to protein receptors on Hosts cell via proteins on tail fibers of phages.
The Phage penetrates the weakened hosts cell wall and cell membrane and injects it DNA, and this disrupts the host cells own DNA(broken up)
- The phages DNA directs the cells metabolism to produce viral components-proteins and copies of the Phages DNA.
- -Bacterial DNA is hydrolyzed into nucleic acids
- useful for constructing viral genomes.
- -Production of capsid proteins, viral proteins and
- enzymes only.
- Is the assembly of newly synthesized viral components into a complete virion.
- -Nucleic Acids are packed inside capsid
- -Capsid is attached to tail
- ***UNTIL MATURATION IS COMPLETE, IT IS NOT A COMPLETE VIRUS!!
- Mature infectious virion partices are released from Host cells to infect new hosts cells.
- -Burst Time
- -Burst Yield
- Is how long it takes to go from Adsorption to Release.
- -(20 -40 min)
- How many phages are released per bacteria.
- Result in the transfer of viral genes to bacterial host (transduction)
- Prophages' genes encode for production of protein that:
- - Repress viral replication
- - Provide "immunity" to infection by related phages.
- - Produce Toxins (ex. C. botulinum, C.diptheriae)
- *Ticking time bomb*
- Can occur Spontaneously or in response to outside stimulation (eg. low iron concentration).
- Prophage removes itself from bacterial chromosome and begins lytic-like process to produce new temperate phages
- Attachment of spikes, capsid or envelope and
- Penetrates via endocytosis or fusion
- Uncoating is necessary when it comes into the cell
- Replication of DNA genome occurs inside the Hosts Nucleus
How viruses cause disease?
occurs when animal viruses undergo Lysogenic replication or when hosts cell lacks materials for lytic replication, slower process and overtime it can reactivate and cause disease (ex. chickenpox to shingles ).
How viruses cause Disease?
Cytopathic effects (CPE)
- effects are directly observable changes to infected cells resulting in abnormal functioning from non infected cells to infected cells.
- -inclusion bodies
- 'viral junk' that remains after infection has resolved(rabies leave junk behind)
- -and can transform normal cells into cancer cells.
- cells that are clumped together and cause a mass (measles)
- a visually observable change
Cancer gene 'on'
Cancer gene 'off'
- Epstein-Barr Virus (EBV)
- Human Papilloma Virus (HPV)
- Herpesviru 8 (HV8)
- Hepatitis B Virus
- Hepatitis C Virus
Is infectious and can cause mononucleosis and is assosiated with Burkitt Lymphoma and Hodgin Lymphoma
can cause benign warts and genital warts, and is associated with Cervical, Penile and Oropharyngeal Cancer
growth in lymph nodes and is associated with Kaposi's Disease
Hep B virus and Hep C virus
cause hepatitis and is associated with liver cancer
- Virus like agents
- are small infectious singular, circular RNA molecules
- does not produce proteins
- pathogenesis is unclear
- presently know to only infect plants
- (ex. Potatoe Spindle Tuber disease)
- Virus like agents that are small proteinious infectious particles that is resistant to heat, disinfectionand radiation.
- they are sensitive to protein denaturing agents (soap) and can cause diseases in humans and animals.
- (ex. Mad cow disease, chronic wasting disease)
an RNA virus genome in the form of mRNA is referred to as?
+ sense RNA
animal viruses differ from bacterial viruses by?
Release of animal viruses occur via lysis or budding; the release of bacterial viruses occur via lysis only.
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