Microbiology Flashcards
virus
- obligate intracellular parasite
- protein + nucleic acid
capsid
- protein shell
genome
- DNA/RNA
- ss or ds
- linear/circular
- CAN’T BE BOTH RNA AND DNA
Two basic steps for viral life cycles
- attachment (adsorption)
- injection (penetration)
lytic life cycle
- transcribe and translate the viral genome
- replicate the viral genome
- replicate capsid
- assemble genome into capsid
- lysis of host cell and release of new viral particles
early genes
- hydrolase
- capsid proteins
hydrolase
- destroy host cell genome (for ds DNA viruses)
transcribe and translate the viral genome
- all cellular energy is now directed to viral protein production
- create a pool of free dNTPs for viral genomes
replicate the viral genome
- assembly with the capsid is automatic
lysis of host and release of new viral particles
- late genes: lysozyme
- punches holes in the bacterial cell wall
- bacterium cannot resist influx of water by osmosis and lysis
lysogenic cycle
- integrate viral genome with host genome
- normal host activity, including reproduction
- excision and lytic cycle
- transcribed and translate repressor which turns off synthesis of viral genes.
excision and lytic cycle
- repressor proteins are removed and the virus enters the lytic cycle due to some type of host cell stress (heat, pH)
productive cycle
- cell without a cell wall
- like lytic but no lysing of host cell
- bud through the cell membrane
- enveloped virus
- coated by lipid bilayer
- animal viruses only
advantages of productive cycle
- get more viruses produced
- envelope
- immune protection
- easier to infect new cells “eclipse” into a new cell. taken up with their capsid and uncoat in a new host cell.
+ RNA viral RNA genomes
- (+) RNA virus: genome acts like mRNA
- Codes for RdRp
- RdRp synthesizes (-) RNA strand from (+)
OR - host cell ribosomes attach and translate (+) to viral proteins
- RdRp synthesizes (+) from (-) to generate more
(-) RNA viral RNA genome
- (-) RNA is template for mRNA
- must carry and code for RdRp
- RdRp synthesizes (+) RNA
- host cell ribosomes translate into viral proteins
OR RdRp synthesizes more (-) RNA
(+) RNA lysogenic
- RdDp (reverse transcriptase) converts into ssDNA
- DNA pol replicates to dsDNA
- insert into host genome
- production of more (+) RNA genome
OR expression of the viral genome in viral proteins
problems with lysogenic virus from human perspective
- permanent in the host cell genome
- rapid mutation
prion characteristics
- no DNA/RNA
- no cell membrane
- no organelles
- very small proteins
- very stable
- resistant to heat, acid, detergent
two categories of prions
- normal prion (good)
- mutant prion (bad)
- spongiform encephalopathies (mad cow)
how to get mutant bad prions
- from mutation
- inherited
- from ingestion of infected tissues
role of mutant prions
- healthy cell transcribing and translating normal “good prion”
- consumption of mutant “bad” prion from diseased tissue
- mutant “bad” prion changes normal “good” prions to bad ones
- mutation in gene coding for mutant “bad” prion
- mutant “bad” prions accumulate and lead to cell death.
viriod characteristics
- circular (+) RNA
- no capsid
- don’t (normally) code for proteins
- base pair with existing RNA
- replicate independently
- mostly plant infectors
bacteria shape
- coccus
- bacillus
- spirilla
gram +
- cell membrane composed of a thick layer of peptidoglycan
- stains purple
gram -
- thin layer of peptidoglycan surrounded by outer and inner membrane
- may contain endotoxin call wall component which can cause an immune response
- stains pink
- tend to be a bit more antibiotic resistance
grow in medium temperature
- mesophiles
grow in hot temperature
- thermophiles
grow in cold temperature
- psychrophiles
obligate aerobe
- uses O2 to survive
- die in the absent of O2
facultative anaerobe
- will use O2 if available
- will use fermentation to survive in O2 is absent
tolerant anaerobe
- If O2 is present it will not use it but it is not harmful
- If O2 is absent it will use fermentation to survive
obligate anaerobe
- If O2 present it will die
- If O2 is absent it will use fermentation to survive.
photo
- converts sunlight to make ATP
chemo
- use chemicals to make ATP
auto
- make your own carbon from CO2
hetero
- get carbon from other organisms
auxotrophs
”-“ means can’t do something
- amino acids - can’t make something
- sugars - can’t metabolize
lag phase
- bacteria are acquiring resources for explosive growth
log (exp) phase
- rapid doubling of population
stationary death
- stationary phase - maximum population that a particular environment can sustain
- more death than growth
F+
- allows for formation of a conjugation bridge so genetic material can be exchange
hfr cells
- high frequency of recombination
- F+ is in the bacterial genome
- the F+ cell undergoes rolling replication
plasmid
- replicate independently of the genome
- used in transformation in the lab
- extra gene package
- may contain antibiotic resistant
plasmid
- 1 circular ds DNA
conjugation bridge
- fragile and doesn’t last long
- like an erection
conjugation
- between F+ and F-
- formation of a conjugation bridge
- genetic material exchanged
- recombination between the old and new genome.
transduction
- removal of a piece of genome during excision
- this can get transferred to next host
- means of acquiring genetic diversity for bacteria
viroid replication
- gets into cell then replicates using rolling circle replication to create (-) RNA
- circularize (-) RNA then using rolling circle to create (+) RNA which will roll themselves up.
- OR use (-) RNA to make linear (+) RNA
conjugation
- big increase in genetic diversity
- does not change population size
