microbio final
Terms
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- two criteria for classiying bacteriophages
- phage morphology and nucleic acid properties
- lytic cycle
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-cycle of reproduction for double-stranded DNA phages
-phage life cycle that culminates with host cell bursting, releasing virions - virulent phages
- phages that lyse their host dring the reproductive cycle
- the one-step growth experiment
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-mix bacterial host and phage
-brief incubation (attachment occurs)
-dilute greatly (released viruses cant infect new cells)
-overtime, collect sample and enumerate viruses - adsorption to the host cell and penetration
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-receptor sites -->specific RECEPTORS on host to which viruses attach
---> specific ATTACHMENT SITES on each virus
(can be proteins, lipopolysaccharides, teichoic acids) - synthesis of phage nucleic acids and proteins
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-SEQUENTIAL process
--->EARLY mRNA synthesis
--->synthesis of proteins that enable T4 to take over the hsot cell
--->phage DNA replication
--->LATE mRNA synthesis (encode capsid proteins and other proteins needed for phage assembly) - how is early mRNA made?
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-some by regular host RNA polymerase
-others by modified host RNA polymerase - what are the concatamers in T4 DNA?
- long strands of DNA consistnig of several units linked together
- T4 proteins that bring about lysis of host
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-endolysin: attacks peptidoglycan
-holin: produces lesion in cell membrane - lysogeny
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-nonlytic relationship between a phage and its host
-usually involves INTEGRATION of phage genome into host DNA
---->PROPHAGE=integrated phage genome
---->LYSOGENS (lysogenic bacteria)= infected bacterial host
---->temperate phages=phages able to establish lysogeny - induction
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-triggered by drop in levels of lamda repressor
---> caused by exposure to UV LIGHT and chemicals that cause DNA DAMAGE
-excisionase (binds integrase and enables integrase to reverse integration process) - lysogenic conversion
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-change in host PHENOTYPE induced by lysogeny
(ex: modification of Salmonella lipopolysac structure/production of diptheria toxin by corynebacterium diptherieae - lambda phage
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-double stranded DNA phage
-temperate phage
-linear genome with cohesive ends - If lambda repressor wins...
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-lambda genome inserted into E.coli genome
(integrase:catalyzes integration)