viruses/bacteria - microbio Flashcards
viruses are…
And their components…
obligate intracellular parasites
Components: protein coat (capsid) + nucleic acid (either DNA or RNA, not both)
tail fibers
part of the phage that recognizes bacteria
2 viral life cycles?
- Adsorption
- injection,
- (for lytic cycle) transcription and translation of virus ‘early genes’
- replication of viral genome
- lysis of host and release of virions
- — - (for lysogenic) integrate viral genome into host genome
- normal mitosis of host cell
- excision (of repressor, thus allowing lytic cycle)
virus ‘early genes’
hydrolase (for destroying host cell genome so all energy devoted to virus, and also to provide free dNTPs)
capsid proteins
provirus/prophage
refers to host genome with viral genome already incorporated
LYSOGEN: refers to the host cell that has the viral genome incorporated
REPRESSOR: gene sequence in viral DNA that keeps it quiet in lysogenic cycle
what may trigger lysogenic turning to lytic cycle
change in pH, oxidative stress; these changes lead to excision of repressor gene
transduction
sometimes, during excision of viral DNA from bacterial genome, a bit of bacteria DNA is excised away too. Then, the virus can transfer genes btw cells
productive cycle
unlike either lytic or lysogenic, cause NO lysis, just BUDDING
This is where virions get coated in host membrane, so only enveloped viruses do this. This evades immune recognition
ANIMAL CELLS ONLY - only these have lipid bilayer
What does ‘+’ sense RNA mean?
same thing as mRNA, that is, RNA that already encodes the necessary information. Called + because it is the same info as the + DNA, or template DNA strand
what enzyme +RNA viruses possess?
RNA-dependent RNA polymerase. It turns + RNA into - RNA, then back into multiple strands of + RNA. This enzyme must come from the virus
-RNA viruses have this enzyme
RNA-dep RNA polymerase. This enzyme translates -RNA into +RNA, then back into multiple -RNA for reproduction.
As with +RNA viruses, the virus not only HAS this enzyme ready, but CODES for it too
reverse transcriptase is a…
RNA dependent DNA polymerase. This is used by RNA viruses that wish to undergo lysogenic cycle (whereas RNA-dep RNA pol is only good for lytic cycle)
retroviruses
rapidly mutate
and get permanently stuck in genome, potentially mutagenic to US
prions
- normal prions
- mutant prions that induce conformational change
they are very small and very stable
they have a long onset time to symptoms
viroids
circular RNA which turns ‘good’ RNA to bad RNA, also interact unfavorably with host protein
no protein capsid
bacteria shapes
coccus - round
bacillus - rods
spirellum - spirals
mono-, amphi-, peri-trichous - # of flagella
Gram + and -
Gram + is purple, has an outermost cell wall with peptidoglycan
Gram - has an outermost cell membrane, thus stains lightly
mesophiles
medium temp bacteria
thermophiles live at hot temp; psychrophiles live at cold temp
aerobic bacteria types
obligate aerobe - must have O2
facultative anaerobe - prefers O2 but will survive
tolerant anaerobe - doesn’t use O2 but can still survive
obligate anaerobe - will DIE in O2
auto vs heterotroph
make your own food from CO2 or get carbon from eating others
auxotroph
arg- bacteria can’t make arginine; lac- ones can’t metabolize lactose
binary fission
mitosis for bacteria, has LOGARITHMIC GROWTH. Initial lag phase, shoot up, plateau, then death stage
Downside: very little genetic diversity
conjugation
the F+ bacterium possess the plasmid (F). It is denoted male. It forms a pilus to give the plasmid to to the female F- bacterium
high frequency recombination
version of conjugation where plasmid, incorporated into genome, is sent over as a whole
periplasmic space
present only in gram negative bacteria; they have a ‘sandwich’ of cell membrane, wall, membrane. Space btw membranes is the periplasmic
opportunistic infections
infection by vectors that have low pathogenicity but can really make a killing when host’s immune system weakened. e.g. wound infection from formerly harmless skin bacteria
endotoxins
produced by Gram + and - upon their death only; whereas exotoxins produced continuously
