Lecture 1: Viruses 1 Flashcards
hookworm
99% of time no symptoms
hook on and feed on blood
big b4 sanitation…pretty much EVERYONE had them
they can crawl 4 feet, so latrine are really deep
enter through skin of feet, leave in feces
CAN cause anemia… its rare
hookworm and allergies
ppl with hookworm have fewer allergies…
because they used to be a part of the normal flora?
mast cells mointor worms and allergies…
hookworms could probably regulate activity of mast cells to make them less reactive
hookworms in the south pre Civi war
the hookworms of the African slaves weree different since Africans and Europeans had been genetically isolated
so hookworms were genetically different
these hookworms caused sudden anemia in Southern US
size of viruses
sub-microscopic… cant see with microscope
virus
infect eukaryotes
bacteriophage
“viruses” that infect bacteria
adenovirus
cold
rhinovirus
cold
chlamydia elementary body
NOT a virus
but its very small and cant live by itself
prions
proteins that cause diseases
NO NUCLEIC ACIDS (no genetic material)
but still infectious
are viruses living?
NO
WHY are viruses not living?
because they DON’T have RIBOSOMES
this means they can’t complete the central dogma
REVIEW SLIDE 5!!
table about bacteria vs. viruses
Bacteria vs. Virus (and chlamydias)
INTRACELLULAR PARASITE?
Bact: NO
Chlamydia: YES
Virus: YES… MUST replicate inside cell
Bacteria vs. Virus (and chlamydias)
PLASMA MEMBRANE?
Bacteria: Yes
Chlamydia: Yes
Virus: NO… but some steal host membrane
Bacteria vs. Virus (and chlamydias)
BINARY FISSION?
Bacteria: Yes
Chlamydia: Yes
Virus: No
Bacteria vs. Virus (and chlamydias)
MOVE THROUGH BACTERIOLOGICAL FILTER?
Bacteria: No
Chlamydia: no/yes (EBs do)
Virus: No
Bacteria vs. Virus (and chlamydias)
Posses DNA AND RNA?
Bacteria: yes
Chlamydia: yes
Virus: NO! one or the other
Bacteria vs. Virus (and chlamydias)
ATP generating metabolism?
Bacteria: yes
Chlamydia:yes/no
Virus: no
Bacteria vs. Virus (and chlamydias)
Ribosomes?
Bacteria: yes
Chlamydia: yes
Virus: NO!
Bacteria vs. Virus (and chlamydias)
Sensitive to Antibiotics?
Bacteria: yes
Chlamydia: yes
Virus: no
Bacteria vs. Virus (and chlamydias)
Sensitive to Interferon (increased activity of proteosome)?
Bacteria: no
Chlamydia: no
Virus: YES
does the ability to use ATP mean something is livng/not living?
NO
its ribosome possession
Minimum requirements of viruses (for the most part)
- have genome (DNA or RNA)
- be able to replicate genome inside cell
- can transcribe and translate its genome
- can assemble into infectious units (virions)
- must be able to get out of the cell
virion
extracellular unit of virus
infectious unit
replicative form of virus inside cell
things LIFECYCLE require
cell
virion
ways virus can get out of cell
budding/eggressing: doesn’t harm host cell
lytic: cell explodes
parts of the virus
- nucleic acid: DNA or RNA… these can be PAMPS if they’re different from normal host cells!
- capsid
- envelopes and spikes
DNA types
single stranded (+) double stranded (+).....can be reverse transcribed
RNA types
Single stranded (+/-)... reverse transcribed Double stranded
“reverse transcribed” RNA
going from RNA to DNA to RNA
“reverse transcribed” DNA
going from DNA to RNA to DNA
+/- and ribosome ability to read mRNA
+ strand… can read mRNA directly
- strand… must make the complement (+ strand) so the ribosome can read the mRNA
capsid
protein coat that covers viral genome IN the virion
protein(s) for attaching to/entering cell
subunit=capsomere
shapes: helical, polyhedral, complex
capsomere
single subunit of capsid
made of proteins encoded with virus genome
may be one or more proteins
Best shape
Icosahedron
20 sides
triangle
really strong and has space inside for genome
Envelope
not all viruses are enveloped
envelope made of lipid, protein, carbohydrate
derived from HOST cell membranes
Purpose: protection from immune system bc it looks like self
Spikes
proteins/carbohydrate complex on virion surface
viral proteins that protrude through the envelope
purpose: adhesion, attachment
Lytic
causes bacteria to lyse so virus can get out
egress
mature virions get out of cell without killing
like secretion system from first exam
lysogenic
(pro)phage or provirus goes dormant and becomes part of the genome
not currently active
Bacterial Phage vs Virus
totally genetically distinct from eukaryotic viruses
evolved separately
same 4 genome types
same capsid, shapes, ways of escaping host cell
lots of separate evolution to icosahedron shape… EFFIECINCY of replication
escaping form Gram negative host bacteria cell
hard to get out because 2 membranes…
EGRESS… make a tube to escape
very similar to type 3 and 4 secretion/flagella
What came first: Flagella or virus
a) flagella may have gotten a genome and escaped
b) bacteria cell may have captured a virus
what is the evolutionary advantage of a bacteriophage
horizontal transfer of genetic material
since bacteria don’t sexually reproduce
what drives viral evolution?
efficiency
ability to evade immune system
Lambda phage
necked virion
virion=no metabolism inside
pin that IDs the right host and pokes a hole in the host
50,000 base pairs (thats a lot)
How does the Lambda phage get the genetic info across the membrane without ATP?
SPRINGS
2 sets:
1) the sitting of the pin to poke the hole, nrg stored in sheets released
2) lack of water in capsid… water enters after poke and the DNA unwinds and enters cell
How does lambda phage find E. coli host?
recognized LamB protein on host surface
molecular pattern recognition like our immune system does
after sitting on host
sheath collapses, nrg release
rehydration of capsid with DNA
genome shoved into host cytosol
after getting in
biosynthesis… transcription by RNA POLYMERASE in bacteria cytosol
copies of genome and proteins made
while copies are being made
lambda phages self assemble
dont need ATP for assembly into cool shape
after self assembly
lambda phage leaves
the head protein of the lambda phage
requires ATP to dehydrate the capisd
dna get wound really tight in absence of water
lytic vs. lysogenic phages of lambda phage
lytic: phage lyses host cell after it uses it
lysogenic: integration into host genome. prophage replicates…
prophage release if cell stress occurs
