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Microbiology Things-to-memorize - summary notes
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11/19/23, 1:21 PM Things-to-memorize - summary notesMisc
What is T symmetry value? E.g. T=7 for bacteriophage.
Differences in template reading:
o Transcription / replication = template is READ from 3’ to 5’.
o Translation = template is READ from 5’ to 3’.
Lec1 – Viral Diversity
How does Circular Transcription Rolling Circle Replication work (RNA-dep RNA poly does this
somehow)
Tropism
Plaque assay
o
Hemagglutination assay
o Dot = no virus
o Blobby mesh = virus
Origin of virus
o Virus-first
Viruses existed before cells as self-replicating units, become more complex until
they themselves became the first cells.
o Escapist / progressive
Viruses originated from RNA/DNA that escaped a host cell and began evolving.
o Devolution / regressive
Complex cells devolved to become virus, losing lots of machinery in the process.
Baltimore classification
o
Lec2 – Plant and Insect Viruses
Viroid
o Rolling circle replication.
Host RNA polymerase binds to the template, and then goes around in a circle,
repeatedly making the genome many times.
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,11/19/23, 1:21 PM Things-to-memorize - summary notes
The multiple genomes are still all in 1 piece (known as concatemer), so there
needs to be a way to cleave it into many genomes.
In viroid, it’s done via ribozymes.
Viroid-like plant satellites
o Needs “helper viruses” to grow.
o HDV (hepatitis delta virus)
Only one known to infect humans… early primitive form of virus that has learned
to jump from plants animals.
REQUIRES HEPATITIS B VIRUS TO GROW!
Can do ORF (open-reading frame) shifting to make 2 proteins from 1 RNA.
Disease
Liver failure
Cucumber mosaic virus
o Genome
Multiple segments of RNA, rather than 1 segment.
1, 2, and 3 are genomic RNA
4 and 4a are subgenomic RNA.
o Translation
Encodes 5 proteins
o Replication
Ends of genome have little cute structures that recruit RNA Polymerase and
RNA Binding Protein.
The latter lets the genome bind to the surface membrane of host.
More RNA-BP binds and allows vesicle thingy to form, allowing for
rolling circle replication to occur.
Baculovirus
o Structure
Enveloped, long rod shape.
Budded form and Occluded form (explained below)
o Genome
Circular dsDNA.
Coiled!
o Temporal regulation of genes:
Immediate early, early, late, very late.
o Budded form
A single virion.
Has an envelope.
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o Occlusion form
Many virions packaged together.
No envelope, but is rather surrounded by a crystalline matrix.
o
o Occluded is eaten by insect.
o Once inside gut cell, matrix dissolves and releases the virions.
o Virions go to nucleus and do replication.
o After it is packaged properly in the nucleus, it leaves nucleus → leaves cell.
Here, it has left the cell in its budded form.
Transmission is cell-to-cell.
o After a long time, it goes another route…
It encases itself into the crystalline matrix & encases that into a polyhedral (the dark-
grey hexagon)
, and then leaves the cell.
Here, it has left the cell in its occluded form.
Transmission is host-to-host
o (plant → insect intermediate (where this all happened LOL) → plant).
Lec3 – Bacterial Viruses
ssRNA bacteriophage
o Genome
Positive-sense (+) ssRNA
o Only affect gram NEGATIVE (-) bacteria.
Binds to their F Pili.
Then maturation proteins can cleave conformation change ssRNA enters
host bacterium.
o Replication
Know this difference:
Transcription / replication = template is READ from 3’ to 5’.
Translation = template is READ from 5’ to 3’.
Replicase == RNA-dep RNA poly.
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