Microbiology Lecture 30: The Viruses Part 2

Front 1

--Propagation of Viruses--

Since viruses are intracellular obligate parasites they lack the BLANK and BLANK to generate energy.

Thus they require a BLANK BLANK and all the enzymes and cell structures for replication.

The BLANK of virus particles requires living host cells.

Back 1

enzymes and components

living host

cultivation

Front 2

What is used to treat Hepatitis C? How does it work?

What is used to treat genital herpes?

Back 2

B-Interferon; it interferes with viral replication, specifically with translation of mRNA.

Acyclovir; a nucleoside derivative

Front 3

Animal viruses are cultivated in BLANK BLANK culture in the lab. Done in a special plastic flask or dish.

A special medium is required made up of what 5 things?

Done in an incubator with BLANK% CO2.

Primary cultures are from the BLANK host tissue, secondary cultures are formed on BLANK.

Some cell lines are famous such as BLANK BLANK which are from Henrietta Lacks and are from cervical tissue.

Back 3

animal tissue

amino acids, vitamins, ions, buffers and animal serum

5%

original; passage

HeLa cells

Front 4

Viruses are propagated in BLANK BLANK eggs 6 to 12 days old by using different BLANK sites.

BLANK are grown in the lab on suitable bacterial host.

BLANK and BLANK are mixed and suspended in a soft agar overlay.

Back 4

chicken embryonated; inoculation

Bacteriophages

Bacteria and the phage

Front 5

How do you assay viruses? What is a downside to this method?

How about bacterial plaques?

What about Hemagglutination assays or viruses that have hemegglutinatin spikes?

Back 5

Count through the use of the electron microscope and count the number on the grid. Does not distinguish live from dead.

Look for clear areas on the bacterial lawn which represent one original phage particle.

Can be assayed using RBC’s that attach to RBC’s and form bridges between the cells. Look for large aggregates at bottom of the plate.

Front 6

--Replication of Viruses multistep process: Early, Middle, and Late--

1. BLANK of the virion to the host (adsorption)
2. BLANK of a virus or its nucleic acid into the cell
3. BLANK of the viral particle and BLANK of viral proteins
4. BLANK and/or BLANK of the new virus particle.
5. BLANK of the mature virus from the host cell.

Steps 1-3 are known as the BLANK phase where no mature virus particles are present and infectivity is lost.

Also see the BLANK of host cell DNA and the shift to the BLANK of viral proteins.

Back 6

1. Attachment
2. Penetration
3. Replication; synthesis
4. Assembly and/or maturation
5. Release

eclipse

degradation; manufacture

Front 7

How do viruses generally enter and infect plant cells?

Back 7

They enter through damaged cell walls.

Front 8

--Infection of the host--

Virus-host interactions are very specific and in bacteria, different BLANK can serve as phage BLANK.

Bacteriophages have specialized structures for BLANK. After attachment, phage's BLANK BLANK is immediately injected into the host cell.

Since animal cells lack specialized receptors, enveloped animal viruses attach to cells via BLANK BLANK.

Enveloped viruses enter the host via the process of BLANK.

The virus is ingested into a BLANK (vesicle inside the cell that is fused with a lysosome), and later the virus is released into the BLANK.

Viruses that lack an envelope penetrate by BLANK or BLANK BLANK through the plasma membrane.

Back 8

molecules; receptors

adsorption; nucleic acid

glycoprotein spikes

endocytosis

phagolysosome; cytoplasm

endocytosis; direct passage

Front 9

If the viral genome is dsDNA, then it replicates by the BLANK BLANK mechanism.

If the virus is a ssDNA virus, the DNA is converted into a BLANK BLANK form by a host BLANK BLANK, but one of the strands is BLANK before assembly of the new particle.

Back 9

Rolling circle

double stranded; DNA polymerase; discarded

Front 10

THIS IS RNA VIRUS REPLICATION!!!!!!!!!

dsRNA (RNA!!!) viruses replicate using the BLANK BLANK mechanism except they use BLANK as precursors.

ssRNA viruses replicate in 2 methods:
1. The viral RNA is copied using a BLANK BLANK to form a BLANK BLANK.

2. Another method the ssRNA genome directly serves as a BLANK for the synthesis of BLANK strand, via a reverse transcriptase.

This DNA is copied to form BLANK

Back 10

rolling circle mechanism; ribonucleotides

viral replicase; complementary strand

template; ssDNA(-); dsDNA

Front 11

--Assembly of the viral particle--

With bacteriophages, it begins with the aggregation of BLANK subunits into complete BLANK.

In some bacteriophages, there are BLANK BLANK involving synthesis of the head, tail and tail fibers.

--------
In enveloped animal viruses, assembly occurs by the wrapping of the host BLANK BLANK around the BLANK BLANK core as it passes through the membrane as it goes BLANK of the cell.

Back 11

capsomere; capsids

separate pathways

plasma membrane; viral nucleoprotein; outside

Front 12

--Release of the viral particle--

The last step in viral replication is BLANK of the intact BLANK BLANK from the host.

Specifically some BLANK are released by the action of BLANK, one of the late proteins encoded on the viral genome.

Most phages are released by a process of BLANK BLANK BLANK and BLANK of the host cell.

Animal viruses are released through BLANK in the cell membrane.

Back 12

release; virus particle

bacteriophages; lysozyme

rapid cell lysis; death.

ruptures

Front 13

What are two consequences of viral infection?

Back 13

Viral cell transformation and Lysogeny

Front 14

What is it called when certain DNA and RNA viral infections result in unregulated cell growth?

Transformed cells can have altered BLANK and demonstrate the appearance of new BLANK. Often they demonstrate the loss of BLANK BLANK.

This prevents cells from BLANK BLANK and results in the aggregation growing into masses of tumors called BLANK. These tumors may be BLANK or BLANK.

In cervical cancer, the cells pick up the BLANK BLANK.

Back 14

Viral cell transformation

metabolism; antigens; “contact inhibition”

growing normally; “neoplasms”; benign or malignant

HPV DNA

Front 15

What is it called when the bacteriophage DNA enters the bacterial chromosome, becomes a BLANK, and gets replicated along with host DNA?

The bacteriophage DNA is transferred to BLANK BLANK. The bacteria said to contain the prophage are called BLANK.

The prophage remains part of the bacterial genome until it is induced to enter a BLANK BLANK.

Some inducing agents are BLANK and BLANK.

Back 15

“prophage”; Lysogeny

daughter cells; lysogenic

lytic cycle

UV light and mitomycin C

Front 16

Some temperate bacteriophages cause phenotypic genes in bacteria like production of toxins. This is called BLANK BLANK.

What 3 pathogenic strains is this seen in?

Back 16

Lysogenic conversion

C. diphtheriae, S. pyogenes, Clostridium botulinum

Front 17

What are two agents smaller than viruses?

Back 17

Viroids and prions

Front 18

BLANK were found in 1961 as agents smaller than viruses that consist only of BLANK BLANK.

The above biological molecules are protected from environmental nucleases because they are BLANK BLANK.

They cause a number of BLANK BLANK but have not been associated with organisms higher than those.

Back 18

Viroids; nucleic acid

tightly folded

plant diseases

Front 19

What are proteinaceous infectious particles called?

What do they cause? What do you observe?

What 2 diseases do these particles cause in humans?

What disease do they cause in cows?

Back 19

Prions

A neurological disease in cows, sheep, goats and deer.

Clinically you observe twitching, itching, eventually paralysis.

kuru and Creutzfeldt-Jakob disease (CJD)

Bovine spongiform encephalopathy (BSE) aka mad cow disease. BSE has been observed in various cattle outbreaks.

Front 20

How long does it take for the prion-caused Creutzfeldt-Jakob disease (CJD) to develop in humans?

What is a specific prion illness that was observed in a group of people that practiced cannibalism?

Back 20

50 years

Kuru