Virology 1 Flashcards
what does a virus being an obligate intracellular parasite mean
- They cannot live independently
- Cannot replicate outside of living cells
what are viruses that infect bacteria called
bacteriophages
whats the extracellular form called & function
- Virion
- Enables transmission to new hosts
5 steps of lytic pathway of bacteriophages
- Attachment
- Penetration of nucleic acid material
- Synthesis of viral proteins & nucleic acids
- Assembly of new viruses
- Cell lysis, release of new virions
explain the lysogenic pathway of bacteriophages
- Integration of viral genome into bacterial host genome
- Virus is vertically transmitted to new daughter cells
- Induction via stress/spontaneously to lytic cycle
What is different when viruses infect eukaryotic cells infect when they infect bacterial cells
Basic steps in infection pathway are the same but the whole virion is endocytosed into the cell
What does Phage Chi bind to
Flagella
What does Phage M13 bind to
Pili
What does Phage MS2 bind to
Pili
What does Phage T1 bind to
OMPs (outer membrane proteins)
What does Phage T4 bind to
LPS
What does Phage Phi174 bind to
LPS
Importaance of receptor recognition (for viruses)
- First step of viral infections of host cells
- Determines host specificity
- Can predict virus host jumps - understand disease outbreaks
Virion function
To deliver the viral genome into a host cell where it can be replicated
What does Herpes Simplex virus 1 cause
cold sores
What does Herpes Simplex virus 2 cause
Genital herpes
What does rotavirus cause and what is its virion called
- Reovirus virion
- Rotavirus causes GI infections, diarrhea & is a major cause of infant mortality in developing countries
What are the reservoir hosts for ebolavirus
Bats
What virus was the great influenza pandemic caused by
The H1N1 influenza A virus
When was the earliest documented case of the great influenza pandemic & where
- March 1918
- In Kansas
Why is the study of viruses NB for crops
- 47% of the pathogens that cause emerging & re emerging plant disease epidemics are viruses
Nutrient Cycling due to viruses - viral shunt in marine ecosystems
- Viruses infect & replicate in bacteria, phytoplankton & other m/os
- Infected cells lyse, cellular contents released, incl nutrients - carbon, nitrogen, phosphorous back into environment
- Nutrients are recycled & used by other organisms
How do lytic phages drive bacterial (host) evolution
By applying lethal selection pressure and driving bacteria to develop resistance
what is the ongoing process of diversification between bacteria and phage populations called
antagonistic coevolution
how do temperate/lysogenic phages contribute to bacterial evolution
Horizontal gene transfer - phages integrate into host genomes
What toxins from pathogens are encoded from/ derived from phages (2)
- Cholera toxin
- Shiga toxin
What are AMGs that phages can encode & their function
- Auxiliary metabolic genes
- Rewire host (bacterial) metabolism - benefits phage
Explain how there is viral sequences in human DNA & what are these known as
- Retroviruses infected germline cells (sperm & egg)
- Incorporation of viral DNA into genome of host
- Viral sequences passed through generations & are present in human DNA
- Known as endogenous retroviruses (ERVs)
Are endogenous retroviruses active
- Inactive/accumulated mutations that make them non functional
- Some may be able to produce proteins/RNA
