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61 Cards in this Set
- Front
- Back
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Where can viruses replicate?
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inside cells whose capabilities they use
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What are viruses also known as?
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bacteriophage or phage
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What forms of life do viruses infect?
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Bacteria, Archaea, and Eucarya
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Why must phages be able to exsist in extreme conditions?
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because some of their hosts are able to live in those conditions and in order to replicate, they must too
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Name the shapes of viruses
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isometric (sphere w/ many triangles)
helical (rod) complex (head + tail) |
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What are the components of a virus?
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Nucleic Acid
Capsid Nucleocapsid Attachment Proteins (spikes) Enveloped |
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What type of structure holds all of the virus' genetic make-up?
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DNA or RNA (but never both)
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Nucleocapsid
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capsid that is mixed with the nucleic acids
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What is the capsid composed of?
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protein subunits called capsomers
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What type of viruses (animal or plant) must be able to attach to specific parts of the host?
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animal
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How are viruses attached to the host in isometric viruses and in complex viruses?
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isometric - by spikes
complex - by tails |
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Naked Virion
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a virus that consists of only the protein capsid
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enveloped virions
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those viruses that have a bi-lipid layer surrounding the capsid
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What is found only in enveloped virions?
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matrix protein right inside the envelope
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Obligate Intracellular Parasites
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viruses that must replicate inside another cell because it does not have the capability to replicate on its own
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What happens to the nucleocapsid right before replication begins?
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it separates from its coat
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What must every virus contain genetic information to encode proteins to do what?
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1. Make a viral protein coat
2. Replicate Viral Nucleic Acid 3. Move the virus in and out of the host cell -and some enzymes that are made by the nucleic acids |
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Name an example of a mimivirus
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acanthamoeba
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Name the unusual features of Acanthamoeba
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largest DNA capsid
large genome encodes for unknown proteins can't replicate |
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List 4 features of viruses that distinguish them from free living cells
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1. they are significantly smaller than free living cells
2. multiply only within cells 3. contain either DNA or RNA, not both 4. lack ribosomes and enzymes for energy |
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Productive Infection
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when viruses invade the host and lyse the cell with more viruses produced
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Name the types of productive infections
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lytic
leaking out temperate (latent state) |
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Latent
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they are able to infect a host without any signs of infections
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temperate
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viruses integrate thier DNA into the genome of the bacteria they infect or the DNA replicates as a plasmid
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lysogen
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bacterium carrying the phage DNA
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What % of phages are temperate?
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90%
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What is the phage DNA called after a temperate DNA is integrated into a host cell's DNA and replicated?
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prophage
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What is another type of latency?
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temperate phages multiplying as plasmids
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What is an example of a temperate phage?
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Lambda (y)
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What is generalized transduction carried out by?
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temperate and virulent phages
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What is specialized transduction carried out by?
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temperate phages
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What is bacteria in Cholera caused by?
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vibro cholera
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What are the symptoms of Cholera?
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severe watery diarrhea
vomiting |
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What was the source of Cholera causing infection?
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fecally contaminated water or foods
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What does bacteria produce in Cholera?
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cholera toxin that causes intestinal cells to continuously secrete chloride ions and electrolytes into lumen resulting in a loss of fluid
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What bacteria does lambda only attach to?
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E. coli
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Name the two pathways that a temperate phage can take?
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Lytic Replication Pathway
Lysogenic Integration Pathway |
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How does a temperate phage integrate its genome into a host DNA?
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through site specific recombination
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What happens to the temperate phage after site specific recombination occurs?
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it will remain in the cell and passed on to daughter cells
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How is latent state replication different from transformation, transduction, and conjugation?
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the phage DNA is added without replacing any bacterial chromosomal genes
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What process is the same in lytic and lysogenic reproduction?
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attachment and entry
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site specific recombination
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specific phage genomes will always insert at the same point
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How do temperate phages deal with a host cell being damaged?
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the ability to swap between lytic and lysogenic pathways
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What must occur to allow a temperate phage to live in the host without replicating its own DNA?
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the temperate phage has a repressor enzyme that represses the genes that control transcription of the integrated cells required for transcription
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What enzyme removes the temperate DNA from the host DNA?
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excisase
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How often does a phage DNA excise itself from the host?
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about 1 in every 10,000 divisions of the lysogen
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Phage Induction
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occurs when host DNA has been damaged (ex:UV light) and SOS is unable to repair the thymine dimers. The temperate phage enters into lytic productive infection leaving the cell
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How does a host cell of temperate phages have a type of immunity?
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their repressor binds to the operator in the phage DNA as it enters the cell and inhibits replication therefore the cell is immune to infection by the same phage, but not different ones
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Lysogenic Conversion
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temperate phages confer new properties on to the cell allowing them to be toxins to non-lysogenic bacteria
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Name some examples of bacteria that temperate phages can make a cell become toxic to
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C. botulinum
Salmonella V. cholerae |
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defective phage in transduction
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during excision, a phage pulls out some of the specific genes and leaves some of his DNA making the phage defective to reproduce
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What type of phage is used in specialized transduction?
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lysogenic/temperate phages
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What is transfered during generalized transduction?
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any host DNA incorporated during assembly
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What is transfered during specialized transduction?
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specific gene and part of DNA during the excision of the prophage
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Who and how many transfers it during generalized transduction?
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phage, some/few pick it up
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Who and how many transfers it during specialized transduction?
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phage, all get the gene
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Can the 2nd phage infected cell produce more phage in generalized transduction?
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No, because he was given host DNA
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Can the 2nd phage infected cell produce more phage in specialized transduction?
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Maybe/No, because it depends on how much genome was picked up (defective phage genome)
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Host Range
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the number of bacterial strains that a particular phage can infect
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What factors limit a host range?
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1. phages must attach to specific receptors on the host cell surface
2. a restriction modification system it must over come |
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How are receptors modified?
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through mutation
through lysogenic conversion |
