Section 3 Final Exam Flashcards
diff of archeal viruses (7 things)
1- encode pesudopeptidoglycan specific lysin enzyme
2- have NO RNA viruses isolated (but maybe identified by metagenomics)
3- have one ss DNA virus (rest are dsDNA)
4- some have circular dsDNA packed in virion (never in phages)
5- many have envelopes
6- released without lysis
7- not pathogens and extremophiles so hard to research
When archeal viruse genomes are sequnced:
most have no similarity to previously discovered genes (similar to well studied phage groups)
Model Archeal virus:
Sulfolobus spindle-shaped virus (SSV-1)
lemone shaped
SSV-1 virus encodes the enzyme ________
reverse gyrase
Function of SSV-1 reverse gyrase:
introduces positive supercoils into DNA protecting it at higher temperatures (common in hyperthermophiles)
SSV-1 is a temperate virus:
1- integrates into host genome
2- gets induced for replication by UV damage or stress
3- goes through round of replication to make and release visions
4- goes back into lysogenic state
SSV-1 type of DNA and TEMPORALLY CONTROLLED transcription:
Tracked expression of genes through infection of cell
dsDNA CIRCULAR (takes 6 hours to transcribe late genes)
T-ind (immediate early)
T5 and T6 (early after 1 hr)
T9 (late early 5 hrs)
Late gene after 6 HOURS
slow development when compared to other viruses (some take 5 min)
Archeal virus circular DNA genomes can be manipulated in vitro (in a test tube and then adding that DNA back into host cell) to study the viruses replication abilities, they found that:
- mutation of many genes still allows for replication
- trend between conservation and essentiality, but not perfect
Another archaeal virus :
Acidianus two tailed virus (ATV)
also lemon shaped
Shape of SSV-1 capsid protein
NEVER SEEN BEFORE 1
4- stranded helices (4 strands of protein come together as one cable)
THEN 6 of these cables wrap around outer surface of the virion capsid and tail)
Conserved
ATV grow tails (elongate outside of the cell when temperature is above 75 degrees)
NEVER SEEN BEFORE 2
Finishes growth and maturation OUTSIDE host cell
ATV infects at ____ degrees (host optimal growth temp) and integrates into host chromosome
85
if ATV infects at suboptimal temp, it leads to
Viral replication and lysis
Lambda
Good conditions —-> replication and lysis
Bad conditions—–> integrate and wait
V.S
ATV
Good conditions (85 deg) —->
Bad conditions (suboptimal temp) —->
ATV
Good conditions —-> integrate 85 deg
Bad conditions ——-> replicate and lyse
Another archaean virus (#3)
sublolobus islandicus rod-shaped virus
sublolobus islandicus rod-shaped virus structure
helical shaped structures with tails at the end
sublolobus islandicus rod-shaped virus shape UPON infection
NEVER SEEN BEFORE 3
viral protien makes unusual pyramid structure on cell surface which open to make holes (like a gate) that the virus is released through
Another archaean virus (#4)
Acidianus filamentous virus 1 (AFV-1)
AFV-1 structure
NEVER SEEN BEFORE 4
hook structure at the end of visions that claws to attach to host cells plius
Another archaean virus (#5)
Sulfolobus turreted icosahedral virus (STVI)
STVI facts to make the particle able to withstand high temp and low pH
- tightly packed structure
- high proline content
- increase in electrostatic interactions in capsid proteins
- increased polar surface
evolutionary adaptations
Why do archeal cells get released without lysing cells?
due to cell wall structures having a wide diversity of structures (don’t have rigid peptidoglycan) so can get out by budding they don’t have to lyse
Cytoplasmic membrane
Surface layer (S-layer)
Protein sheath
glycocalyx
lipoglycan
methanochondrotin
peseudomurein
are there RNA archeal viruses
metagenomic evidence:
concentrated viruses from acidic hot springs (environment dominated by arches) isolated nucleic acids and looked for high amounts of RNA
- and RT-PCR found RdRp enzyme sequences
