Chapter 31 - Intro to Virology and Phage Flashcards
describe viruses
- simple organization
-DNA or RNA genome - unable to reproduce outside of living cells
- obligate intracellular parasites
describe cellular organisms
- complex organization
- DNA genome and RNAs
- carry out cell division
- some are obligate intracellular parasites
what are the 3 theories of viral origin
- reductive origin: viruses evolved by degenerative evolution from intracellular parasitic cells
- theory of intracellular origin: viruses evolved from functional parts of cells that acquired an ability to reproduce themselves uncontrolled by the cell
- theory of independent origin holds that viroid nucleic acids could have evolved outside of cells during the RNA world and acquired the ability to infect cells
how big are pandoraviruses
1000nm
what is the biggest virus
pandora virus
multicomponent viruses genomes are segmented and the segments are distributed into _____
separate viral particles
cultivation of viruses requires inoculation of living host cells. what are examples of the host cells
- suitable animals
- embryonated eggs
- tissue cultures
- cytopathic effects (CPEs)
what can tissue (cell) cultures be
- monolayers of animal cells
- plaques: localized area of cellular destruction and lysis
what are cytopathic effects (CPEs)
microscopic or macroscopic degenerative changes or abnormalities in host cells and tissues
what makes up a nucleocapsid/naked capsid virus
- DNA or RNA + structural proteins +/- enzymes and nucleic acid binding proteins
what makes up an enveloped virus
nucleocapsid + glycoproteins and membrane
what makes up icosahedral symmetry
- nucleocapsid made of
- capsid
- capsomers
- nucleic acids
what virus has icosahedral capsid symmetry
herpes
what is an example of a virus with helical symmetry
ebola virus filaments (SEM)
what do enveloped viruses have vs nonenveloped
glycoprotein spikes and lipid bilayer
what is an example of an asymmetrical virus
vaccinia poxvirus
what are the groups of RNA viruses
nonenveloped vs enveloped
what are the groups of nonenveloped RNA viruses
-single stranded positive sense
- double stranded
what are the groups of enveloped RNA viruses
-single stranded positive sense
- single stranded negative sense
- retrovirus
what properties are used to classify viruses
- type and structure of nucleic acid used for viral genome
- presence or absence of envelope
- type of capsid symmetry
- replication strategy
what are the groups of DNA viruses
nonenveloped and enveloped
what are the groups of nonenveloped DNA viruses
- single stranded linear
- double stranded linear
- double stranded circular
what are the groups of enveloped DNA viruses
- double stranded linear
- double stranded circular
what are the steps of virus replication
- adsorption
- penetration and uncoating
- synthesis of viral proteins and nucleic acids
- assembly of virons
- release
what is adsorption of virions
viral surface proteins and/or enzymes mediate attachment to specific host receptors
what are the 3 mechanisms of penetration and uncoating
- injection of nucleic acid
- fusion of envelope with host membrane
- endocytosis
describe the assembly of virus capsids
- capsid proteins: encoded by late genes
- assembly of naked viruses: empty procapsids formed then nucleic acid inserted
- assembly of enveloped viruses: similar to assembly of naked viruses
- site of morphogenesis varies
describe virion release of naked viruses and enveloped viruses
- naked viruses: usually by lysis of host cells
- enveloped viruses: formation of envelope and release usually occur concurrently
what are virus encoded proteins incorporated into
host membrane
what are the virus replication events during a single infectious cycle
- attachment
- disassembly
- replication
- assembly
which type of infection has the highest number of virus in tissues: acute, chronic or latent
acute then chronic then latent
what are other principles of viral disease
- viral spread and replication
- host factors in defense and damage
- diagnosis
- emerging viruses
are bacteriophages a part of the human virome
yes
what is the bacterial product from prophage “phage C1”
botulinum toxin
what is the bacterial product of beta phage
diptheria toxin
what is the bacterial product of epsilon 34
LPS synthesis
what is the human protein or regulator provided by HERV-W
syncythin 1
what is the human protein or regulator provided by HERV-E
apolipoprotein C1
describe the bacteriophage replication cycle: slow release
a filamentous phage produces phage particles without lysing the cell
- the host continues to reproduce itself but more slowly than uninfected cells because many of its resources are being used to make phages
what are the bacterial defenses against bacteriophages
- genetic resistance- mutations in bacterial genes
- restriction endonucleases- enzymes that cut invading DNA
- CRISP- a bacterial immune system
why is phage therapy being explored as antibiotic treatment
- phages may limit bacterial numbers to levels that the immune system can tolerate
- phage particles may modulate immune system activity
- phages may attack biofilms
