viruses/bacteria - microbio

Question 1

viruses are…

And their components…

Answer 1

obligate intracellular parasites

Components: protein coat (capsid) + nucleic acid (either DNA or RNA, not both)

Question 2

tail fibers

Answer 2

part of the phage that recognizes bacteria

Question 3

2 viral life cycles?

Answer 3

1. Adsorption
2. injection,
3. (for lytic cycle) transcription and translation of virus ‘early genes’
4. replication of viral genome
5. lysis of host and release of virions
   - —
6. (for lysogenic) integrate viral genome into host genome
7. normal mitosis of host cell
8. excision (of repressor, thus allowing lytic cycle)

Question 4

virus ‘early genes’

Answer 4

hydrolase (for destroying host cell genome so all energy devoted to virus, and also to provide free dNTPs)
capsid proteins

Question 5

provirus/prophage

Answer 5

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

Question 6

what may trigger lysogenic turning to lytic cycle

Answer 6

change in pH, oxidative stress; these changes lead to excision of repressor gene

Question 7

transduction

Answer 7

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

Question 8

productive cycle

Answer 8

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

Question 9

What does ‘+’ sense RNA mean?

Answer 9

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

Question 10

what enzyme +RNA viruses possess?

Answer 10

RNA-dependent RNA polymerase. It turns + RNA into - RNA, then back into multiple strands of + RNA. This enzyme must come from the virus

Question 11

-RNA viruses have this enzyme

Answer 11

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

Question 12

reverse transcriptase is a…

Answer 12

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)

Question 13

retroviruses

Answer 13

rapidly mutate

and get permanently stuck in genome, potentially mutagenic to US

Question 14

prions

Answer 14

1. normal prions
2. mutant prions that induce conformational change
   they are very small and very stable
   they have a long onset time to symptoms

Question 15

viroids

Answer 15

circular RNA which turns ‘good’ RNA to bad RNA, also interact unfavorably with host protein
no protein capsid

Question 16

bacteria shapes

Answer 16

coccus - round
bacillus - rods
spirellum - spirals
mono-, amphi-, peri-trichous - # of flagella

Question 17

Gram + and -

Answer 17

Gram + is purple, has an outermost cell wall with peptidoglycan
Gram - has an outermost cell membrane, thus stains lightly

Question 18

mesophiles

Answer 18

medium temp bacteria

thermophiles live at hot temp; psychrophiles live at cold temp

Question 19

aerobic bacteria types

Answer 19

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

Question 20

auto vs heterotroph

Answer 20

make your own food from CO2 or get carbon from eating others

Question 21

auxotroph

Answer 21

arg- bacteria can’t make arginine; lac- ones can’t metabolize lactose

Question 22

binary fission

Answer 22

mitosis for bacteria, has LOGARITHMIC GROWTH. Initial lag phase, shoot up, plateau, then death stage
Downside: very little genetic diversity

Question 23

conjugation

Answer 23

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

Question 24

high frequency recombination

Answer 24

version of conjugation where plasmid, incorporated into genome, is sent over as a whole

Question 25

periplasmic space

Answer 25

present only in gram negative bacteria; they have a ‘sandwich’ of cell membrane, wall, membrane. Space btw membranes is the periplasmic

Question 26

opportunistic infections

Answer 26

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

Question 27

endotoxins

Answer 27

produced by Gram + and - upon their death only; whereas exotoxins produced continuously