microbiology - viruses, prions and viroids Flashcards

PARTICLES, that are infectious agents and are obligate intracellular paracites because they need a host cell to replicate

host cell. (very strict and eukaryotic cell viruses cannot affect prokaryoticand vice versa. only exception is rabies

1.nucleic acid core/genome- either DNA or RNA genetic material that can be used to classify viruses
2.capsid-protein cote that surrounds nucleic acid core

1.envelope- membrane like structure that surrounds capsid. they sometime steal the membrane from their host cell but they do not function as such
2. spikes-made of glycoprotien and are associated with enveloped viruses. function as attachment to host cell

they are the largest and pretty much self sufficient. size matters .they have multilayered capsids and make own envelope

1.icosahedral/ spherical
2.helical

polyhedron with about 20 equilateral triangular faces. shape of a capsid

cylindrical-tube-like structure

usually spherical however shape of capsid underneath can vary

fully assembed virus particle ; extracelluar form of virus

genome and capsid

a virus with an envelope

not surrounded by an envelope

viruses that affect prokaryotic cells( means bacteria eating)

cell replication=1 to 2
viral replication= 1 to many

advantages-monkeys are close to human,s some viruses wont replicate unless in live animal, good for when we want to see effect on entire animal
disadvantages-very expensive, pediree (not working with genetially identical) and dont know genentic composition, with monkeys they come from other parts of the world and they can be different. also ethics is a factor

adv. they will be like they would be in the animal. you can control / maintain to a certain extent. dis- sacrifice animal, expensive and most organs dont cooperate

fertalized eggs typically chicken eggs. 1st type of test outside original viral place
adv. - cheap, different tissues in egg, viral propigation .
disadv- innoculating egg is not easy. cant’ see what is going on

take cells (animal cells typically sticky) place in glass or plastic container. cells attach to bottom. then baith cells with some kind of medium
two types:
continuous cell lines
primary cell lines

can be transferred indefinitely take growing cells in fresh container and medium and they will continue to grow) adv. passed indefinitely . disadvantage- tend not to be normal cells, eg. cancers. often form monolayer but these don’t

cells that come directly from host- adv. normal cells disadv- transfered indefinitely

the barrier is plant cell wall because viruses can’t get inside by on their own and do so via storm damage insect damage, disease damage and things like that. once affect, spread quickly! shead in seeds

-whole plant cultures
-plant cell protoplast
-plant tissue culture

rub stem and leaves with virus and abrasive material

plants w/o cell wall

adc- cheaper and replicate faster and get more. genetically engineer

methods used “enumerate” viruses

1.hemagglutination assay
2.plaque assay

for animal viruses useful only w/ viruses w/ hemagglutininc causes red blood cells to clump together (you have to have something to hold them together)

1.serially dilute viruses suspended in wells of microtiter plate
2.add same concentration of sheep red blood cells to each well
3.look for hemagg. ( if occured virus particle allows rbs to connect to another virus well and look like they are holding hands. if not occurred all break apart and there is a red dot at the bottom. titer=reciprocal of greatest dil. of virus that allows for hemagg. disadvantage is you cannot cannot compare titer of different viruses. used to monitor viral loads

for bacterophage that lyce host cells.

serially dilute in suspended mix each solution to generate bacteria lawn incculate and count number of plaquest in bacteria. lawn and multiply diltion factor . disadvantage is that you can under estimate

-productive response
-non productive response

-non- integrative lysogeny
-persistent or chronic viral infections
-latent virus infection

when virus successfully infects host cell, begins to replicate and continue to, proglenine are produced and released from cell. length varies

sucessfully inects ,begins to replicate but replication stops. host cell still infected but virus will not kill cell

virual DNA does not integrate but stays in cytoplasm

slow productive response. infect host cells and begin replicating but it takes a long time (examples-1. hepatitis b. virus - not food born, blood born, and sexually transmitted. sometimes never goes away 2-mesles virus (rubeola) incubation period ~ 1 month. 2- epstein - barr virus (herpes virus) . causes mono )

infects then goes dorment but may begin replicating again.( ex. herpes simplex virus type I and II.type 1-> cold sores/ fever blisters. type-> genital herpes infected for life . 2->varicella -> zoster virus - chicken pox and shingles)

lytic cycle
. they lice cells open they kill them but not necessarily lice them

adsorption- host range is defined.. very specific pairing of host and virus. if it does not pair correctly, virus will not affect. virons (use fibers) attach proteins specifically interact with host cell receptor. cell walls are typically receptors (pili, flagella) for animals glycoprotiens

penetration and uncoating- virus gets into cell and viral genome is released. occur simultaneously for bacteriophage(s) φ-> inject genome (usually all that enters) some φ-> genome inserted into bacteria cell wall for all phage the only thing that enters is genome. animal virus-. (endocytosis) membrane fusion event. fusion of envelope with some membrane of the cell via fusion protien and nuclieocapsid is entered. fusion proteins remain at surface and due to bumping cells fuse to each other. uncoating step varies

replication (synthesis)- varies from virus to virus . always occur during “eclipse phase” - time in viral replication when virus has been taken apart. does not always start here. for φ starts at penetration. (stepwise and sequential)
early functions: early mRNA ->early proteins (nucleiaces: shut down factory; polymerase)
late functions:late mRNA-> late proteins (caped proteins , spike proteins etc)

assembly (stepwise and sequential) maturation genome is replicated, build capsid, genome is stuffed, other parts are added if needed some viruses have to get an envelope

release- getting bacteria out of host cell
φ late proteins endolysin
animal vir-> varies considerably some have to just sit and wait. some acquire envelope s they leave or exocytosis.

lysogeny λ . everything goes a planned until replication stops λ jumps into bact chromosome

absorption- λ example-e. coli virus

penetration and uncoating

replication begins

if lysogeny occurs-> integration. λ DNA plants itself inside e. coli chromosomes. λ DNA is replicated along with bacteria chromosome indefinitely

induction- lytic cycle (activity repressor) was keeping it off

replication continues

assembly of virus particles

release of virus particles

early protiens called λ repressor is made λ repressor blocks lytic cycle . when in effect w. coli , has two options- go productive ( lytic cycle ) or non-productive (lysogenic cycle) if enough repressor is made->lysogeny occurs

if the cell is healthy or not

naturally occurs due to nutrient limitation and damaged DNA
in lab-> induction of lytic cycle w/ agents that damage DNA
as a result of DNA Damage bac. cell produces a protease. it cleaves (a different) repressor of a DNA repair system an it turns on
bact protease also cleaves λ repressor
lytic cycle is turned on

only capable of entering productive response. ex. -> cold viruses (rino-virus)

capable of entering non-productive response

bacterial cell infected (dormantly) w/ φ; have medical significance

because of intamacy with its host cell. you cant use antibiotics because they target certain things.

antivirals

revents influenza A by blocking penetration and uncoating steps

nucleotide mimic. herpes virus

to block herpes virus DNA polymerase since they have it and humans don't and used for shingles

used for HIV . works because HIV is a retrovirus

due to reverse transcriptase which AZT targets

chemicals produced by cells

produced by mammals . it is an immunoregulatory molecule
produced in response to double stranded RNA (some viruses have it), endotoxins (LPS) ,some viruses and other antigenic stimuli (something that can turn on a viral response)
function against viruses: cells virually infected prod. interferon whic triggers other cells to produce antiviral molecule * esp RNA viruses because they replicate in cytoplasm

in response to double stranded RNA which is found in some virues, endotoxins (LPS), some viruses and other antigenic stimuli

interferon functions against viruses . the cells virually infect produce interferon which triggers other cells to produce antiviral molecule *especially RNA viruses becaue they replicate in cytoplasm

they are host specific but not virus specific

uncontrolled cell growth; cell cycle is no longer properly regulated

a lump or mass of cells growing out of control

a noncancerous , non-spreading tumor

a cancerous tumor and cells are spreading (metastasis)

-mutagenic agent
-carinogenic agents
-viruses

induce mutations above spontaneous mutations and lead to cancerous conditions

potential to cause cancerous conditions

DNA viruses and long term viruses

tell cells to divide and induce S phase and is very dangerous

sexually and they are benign warts which lead to cervial cancer

fever blisters that lead to lip or mouth cancer

genital herpes that lead to cervical and penile cancer

mono which leads to hodgkins disease and burkett's lymphoma

which is usually found in tropical parts of the world . it is usually a tumor in the jaw but is very treatable

a feaver and a rash that is very prevalent and usually infects in childhood

cancer of vascular epithelial tissue

risk of liver cancer

some retroviruses and HTLV i and HTLV II ( human tull lymphotropnic virus and some are associated with leukemia

piece of circular RNA

plant patogen.

plant cell nucleus

it blocks mRNA splicing

pieces of proteins ( a proteinaceous infectious particles

mammals

(coded for by host) they are misfolded protien and presence of one can cause others to misfold (we think) and causes tangles and kills them (most are not mutants

krutz-jacob disease (KJD)