Microbiology Exam 3

Front 1

Virus

Back 1

replicate in cells, but have extracelluar state

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Virion

Back 2

complete viral particle;
nucleic acid surrounded by a protein coat and in cases other material

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Infection

Back 3

virus enters a cell in which it replicates. Infected cell is the host

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Virus genetic material

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DNA or RNA, rarely both together
circular or linear(can be segmented)
single or double stranded

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Virus structure

Back 5

surround genetic material with a capsid
Individual proteins are: capsomers or protomers

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nucleocapsid

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complex of genetic material, viral enzymes, capsid together

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envelopes

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surround nucleocapsids
most, but not all have envelopes
lipid bilayer membrane(derived from host cell, while coded in viral genome) w/ integrated proteins
names: Hemagglutinin, Neuraminidase

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Capsids

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protect viruses
high affininty for other capsids proteins, hard to separate in native form
this allows coagulation and form a rigid protective coating

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Icosahedrons

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capsid symmetry
2, 3, 5, 6 fold axis of symmetry
faces are triangular in shape
made up of 3 capsomers

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parvovirus

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DNA without double strand

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Viral genomes code for

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enzymes or receptors for infection and replication

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Viral genomes

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few structural genes, b/c they use polymers made from the same protein subunit throughout to form their capsids

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size of viral genomes

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significantly smaller than any live organism

genome for K-12 strain of E. coli is 400 times larger than the genome of phi-chi-174, one of its viruses

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viral growth cure

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has 4 stages, same general shape as bacterial growth curve

begins - virus enters host
ends - when it is released

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Viral growth plot

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ATTATCH, Eclipse, Maturation (Rise), Release ~ 15 hours

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viral attatchment

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recognize host via receptors on membrane

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Viral penetration

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1) Direct injection
2) Adsorption
3) Endocytosis

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Direct injection

Back 18

inject viral DNA from capsid through membrane host

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Adsorption

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fusion of the viral envelope to the CM

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Endocytosis

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vesicle mediated entry to the cell via receptors.
Naked and Enveloped viruses use this strategy

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Eclipse

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viral particles have entered, but undetectable

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Rise

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viral particles detecable as they replicate

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Release

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virions exit by budding, or cell lysis
Envelope viruses exit by budding, and retain some host cell membrane

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Latent infection

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virus present but no harm, can be activated

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Acute infection

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Rapid multiplication, cell death and virus release

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Chronic infection

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slow release of virus w/o cell death

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Transfor into malignant cell

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Activation of host proto-oncogene

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Bacteriophage

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virus infects bacterial hosts

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Phage replication

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lytic cycle, ends in cell lysis

also enter lysogenic cycle

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lysogenic cycle

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phage's genetic material is integrated into the chromosomes

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prophage

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phage's genetic material integrated into the chromosome

exist as plasmids in host's cytoplasm

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temperate phage

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genome is able to replicate along with that of its host and NOT cause cell death; called lysogeny

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virulent phage

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lysis or kills host cell after infection: nontemperate

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lysogen

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bacterium containing a prophage

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lysogenic to the lytic cycle

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induced under cell stress

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early genes
&
late genes

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Genes expressed early during infection

genes expressed near the end of infection

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MOI (multiplicity of infection)

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amount of infectious virus absorbed

Front 38

Quantification

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mix phage with host's, after incubation lawn of cells will grow in agar, and Plaques, or holes will represent on viral particle, plaque forming unit (pfu)

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alpha-proteins

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product of immediate early genes

stimulate transcription of early genes

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beta-proteins

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products of early genes


DNA replication, yielding concatemeric DNA. Late genes transcribed

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gamma-proteins

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products of late genes

virion assembly

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DNA viruses

Back 42

replicate in nucleus

Front 43

RNA viruses

Back 43

replicate in the cytoplasm and bring their own replication enzymes within nucleocapsid

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virus Order

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nucleic acid type

Front 45

virus Family

Back 45

replication strategy and morphology

Front 46

virus Genus

Back 46

small genomic differences

Front 47

virus Species

Back 47

not well classified

Front 48

virus and biotech

Back 48

vaccines, gene therapy, gene cloning

Front 49

Viruses exchange btw two different host cells

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via Transduction

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Generalized transduction

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host DNA is inserted into new viral capsid, then into another host cell. no viral infection.
possible homologous recombination

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specialized transduction

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prophage exits lysogenic cycle carrying part of the bacterial chromosome

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viroid

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circular, single-stranded RNA
cause Plant diseases

ex:coconut cadang cadang
citrus exocrotis
potato spindle tuber viroid

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viroid entry

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through wounds

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virus Order

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nucleic acid type

Front 55

virus Family

Back 55

replication strategy and morphology

Front 56

virus Genus

Back 56

small genomic differences

Front 57

virus Species

Back 57

not well classified

Front 58

virus and biotech

Back 58

vaccines, gene therapy, gene cloning

Front 59

Viruses exchange btw two different host cells

Back 59

via Transduction

Front 60

Generalized transduction

Back 60

host DNA is inserted into new viral capsid, then into another host cell. no viral infection.
possible homologous recombination

Front 61

specialized transduction

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prophage exits lysogenic cycle carrying part of the bacterial chromosome

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viroid

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RNA, Naked, circular, single-stranded

cause Plant diseases

No Capsid

ex:coconut cadang cadang
citrus exocrotis
potato spindle tuber viroid

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viroid entry

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through wounds

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siRNA

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pathogenesis from interfering RNA created from the viroid.

prevent host mRNA from being translated. = Gene Silencing

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virusoid

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single-stranded, circular RNA dependent on other viruses (satellites)

RNA codes for structural proteins

same size as viroids

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Prions

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infectious agent of entirely mis-folded protein

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prion examples

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scrapie from sheep
mad cow disease,
kuru
CJD

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Prion generation

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mis-folding of naturally occurring peptides.
Initial prion causes conformational change in the healthy peptide, causing it to fold

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Prion location

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neuron cells of animals
Transmissible Spongiform Encephalopathies (TSEs)

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How get prions

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consume neural tissue of infected individual, spinal fluid

cross species barrier with high homology, but not less genetically alike.

ex prions of bovine infect humans but not mice

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Papillomavirus

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non-enveloped
common in developed countries
also cause of non-genital warts

vaccine is dsDNA

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Influenza

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RNA virus w/ 8 segments
able to recombine w/ other strains its genes making an ultimate vaccine impossible

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Influenza A

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most gentically diverse and most virulent

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Influenza C

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least diverse and least virulent

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Influenza B

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middle ground compared to A and C

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Antigenic shift

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genetic material is repackaged differently in the nucleocapsid to form a new strain. Major Change

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Antigenic Drift

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point mutations and small genomic events happen. Minor Change

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Most common changes occur for Influenza

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in the envelope proteins
hemagglutinin
neuraminidase

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Oseltamivir and zanavir

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neuraminidase inhibitors

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sequence of Influenza

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virion buds out of host,
envelope protein (hemagglutinin binds to complex on host cell consisting of a receptor coupled with sialic acid.

neuramininidase cleaves connection and allows virion to float away from cell

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Hep A

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Picornavirus, ssRNA, non-eveloped virion

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Hep B

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Hepadnavirus, dsDNA, enveloped virion

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Hep C

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ssRNA, enveloped virion

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Hep D

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stellite virus, co-infection w/ Hep B, ssRNA

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Hep B causes

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cirrhosis and liver cancer

Hep C is same with no vaccine

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Herpesvirus

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linear dsDNA
virion surrounded by envelope
in nerve cells of host
DNA can remain premanently outside of the chromosome

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HSV1

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oral

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Herpesvirus

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varicella - chicken pox/shingles

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HSV2

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genital

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Epstein-Barr

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infectious mononucleosis (mono) & respiratory cancer, and lymphoma in AIDS patients

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Cytomegalovirus

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viral pneumonia
oral or sexual transmittance
cause abortions

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Herpesvirus Drugs

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Acyclovir
Valacyclovir

Front 93

Acyclovir

Back 93

inhibits viral DNA synthesis
becomes phosphorylated by thymadine kinase
replaces dGTP in replicating DNA

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common cold

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RNA viruses

rhinovirus
coronavirus
adenovirus

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rhinovirus

Back 95

epithelial cells through ICAM (intercellular adhesion molecule)

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Zinc

Back 96

block rhinovirus receptor

Front 97

Measles, Mumps

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RNA viruses
paramyxovirus

Measles - airborne

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Rubella

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togavirus

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Mumps

Back 99

swelling salivary glands, neck, and jaw.
inflammation of testes and sterility
encephalomyelitis