Microbiology Final

Step 3

Which step(s) in the figure below is/are targeted by antiviral medications such as acyclovir, ribavirin, and AZT?

Generalized transduction occurs when

a bacteriophage packages a piece of bacterial DNA during replication.

During maturation or formation of phage particles

a few phage heads may surround fragments of host bacterial DNA.

when an extensive amount of experimental evidence supports a hypothesis, the explanation may become

a scientific theory

The basic parts of a bacteriophage are

an icosahedral head, tail, tail pins, and fibers.

Antibiotics that target which of the following would be effective against viruses?

antibiotics are not effective against viruses

Viral spikes

attach specifically to host cell receptors.

microorganisms lack a membrane bound nucleus

bacteria and archaea

what is the difference between archaea and bacteria?

bacteria possess peptidoglycan in their cell walls whereas archaea do not

the process by which microbes carry out the decomposition of harmful chemicals

bioremediation

If you can block the effect of HIV protease, you will

block cleavage of the HIV polyprotein into individual proteins.

After entry of the bacteriophage into the host cell, a phage enzyme

breaks the host DNA into fragments.

When the bacteriophage transfers bacterial DNA into a recipient bacterial cell, this DNA

can integrate into the chromosome.

viruses are not microorganisms because they are not

composed of cells

The term "latent" is used to describe some of the HIV virus inside of infected host cells because

double-stranded viral DNA (provirus) is inserted into the host RNA.

The provirus state exists when

double-stranded viral DNA is integrated into host cell chromosome.

Every virus particle contains ______.

either DNA or RNA

Please choose the term that describes a virus that has a lipid bilayer (derived from the host cell) surrounding its capsid.

enveloped virus

If the virus is present as a provirus in the host cell, it remains latent and never produces new virus.

false

Viruses are able to multiply inside a non-living cell.

false

Generalized transduction involves the transfer of phage genes from one bacterial cell to another.

false, The genes that are transferred are bacterial genes.

The minimum bactericidal concentration is determined by

finding out how many live organisms remain in tubes that showed no growth in an MIC test

The HIV protein that is involved in attachment of the virus to host cells is ______.

gp120

The two viral proteins inserted into the host cell membrane as the virus buds out of the cell are gp41 and ______.

gp120 and gp41 are inserted into the host cell membrane, creating the spikes of the virus before the core of the virus buds out.

Protease inhibitors ______.

inhibit processing of long polypeptide chains

An AIDS/HIV patient in need of a bone marrow transplant receives one from a donor who is CCR5 negative (lacks CCR5). If the procedure is successful, this would result in the HIV patient producing CCR5-negative white blood cells. This is beneficial to the patient because CCR5

is a co-receptor for HIV, so infection of white blood cells by the virus is impaired. -Recall that HIV does not infect red blood cells. Also, it requires both a CD4 receptor and a co-receptor for entry into a host cell. If a co-receptor is lacking, the virus cannot enter the cell.

Place the following steps of animal virus replication in their correct order: 1. release 2. adsorption 3. assembly 4. uncoating 5. synthesis

2: Adsorption 4: uncoating 5: synthesis 3: assembly 1: release

Which of the following is NOT a class of antiretroviral medications currently available for HIV-positive individuals?

Envelope inhibitors

What are the two entry mechanisms used by enveloped viruses?

Enveloped viruses enter a host cell by fusion or by endocytosis.

All viruses can infect any cell type or tissue type.

False

Antiviral medications that interfere with genome integration will be useful against all animal viruses.

False

Generalized transduction is so called because specific bacterial genes are transferred during this process.

False, In generalized transduction, any segment of bacterial DNA can be transferred. During specialized transduction, specific genes are transferred, depending on where the viral DNA is integrated into the bacterial chromosome.

The Gardasil 9 vaccine prevents infection by all types of human papillomaviruses.

False, The Gardasil 9 vaccine prevents infection by types of HPV that are linked to developing cervical cancer. There are more than 100 types of HPV.

Which of the medications mentioned inhibits DNA polymerase?

Foscarnet

In order to make the second strand of DNA when HIV starts replicating inside of a cell,

HIV RNA is broken down as it is converted into DNA, leaving a single-stranded DNA template which is used to make the second DNA strand.

Which cells possess the receptor complex for gp120, resulting in their destruction and the overall loss of immune function seen in AIDS?

Helper T-cells and macrophages

Of all the antiviral medications mentioned, which is actually produced by the host?

Interferon

Consider the figure below, which shows MIC results for organism C against antibiotic P. The organism does not grow in the tube containing 16 μg/mL of the antibiotic, and yet it might still be considered resistant to the medication. Why is this so?

It is possible that the maximum safe level of this medication in vivo is less than the MIC, so the antibiotic could not be used at the indicated concentration.

Bacteriophages involved in generalized transduction are ______ phages.

Lytic

Explain the difference between MIC and MBC.

MIC is the minimum dose of an antimicrobial medication that prevents the growth of an organism, while MBC is the minimum dose of that medication that kills the organism.

Antiviral medications that interfere with viral nucleic acid synthesis often appear very similar to which compound?

Nucleosides

During which stage of viral replication does amantadine exert its inhibitory effect?

Penetration and uncoating Correct

What makes phages so specific in their host range?

Phages attach to receptors on their host cell; if a cell lacks those receptors, the phage cannot infect it.

Viral capsids are composed of ______.

Protein

During viral infection of a host cell, which is the third step of the process?

Release of nucleocapsid into host cytoplasm

What is the function of the reverse transcriptase enzyme?

Reverse transcriptase synthesizes DNA from RNA. Retroviruses such as HIV have this enzyme.

HIV, and related viruses such as HTLV, possess which unusual virally-encode enzyme?

Reverse transcriptase: an enzyme that makes double-stranded DNA from single-stranded RNA, is characteristic of HIV and other retroviruses.

In transduction, bacterial DNA is transferred to a new cell when

it is injected by the virus.

The ability of HSV-1/HSV-2 to hide out in nerve cells for long periods of time is known as

latency

The types of cells infected by HIV are ______ early in the course of an infection and ______ later in the infection cycle.

macrophages; helper T cells -The cells infected by HIV are the CD4+ cells: macrophages (first) and helper T cells (later).

When present, of what is the viral envelope composed?

mainly lipids

organisms that populate the human body and which protect it from disease are termed?

microbiota

Bacteriophages adsorb or attach

only to members of the same bacterial species.

A__________ is the term used for any disease causing microorganism

pathogen

After host cell DNA is broken down by a viral enzyme

phage DNA is replicated and phage coat proteins are produced.

A difference between plasmids and fragments of DNA that have been transferred between cells is

plasmids can replicate independently.

If you look inside the core or capsid of HIV, you will find three enzymes: reverse transcriptase, integrase, and ______.

protease: functions late in HIV replication.

HIV attaches to host cells by binding to

receptors

What group of viruses does HIV belong to?

retroviruses

The HIV enzyme that makes a double-stranded DNA copy of the viral genome is

reverse transcriptase.

Proteins that project or stick out from the envelope of HIV and attach or adsorb it to host cells are called ______.

spikes

to indicate slight differences, members of the same species may be given

strain designations

The advantageous genes that can be transferred by transduction are genes for

sugar fermentation. toxin production. drug resistance.

the human body and its microbial inhabitants can best be compared to

the earth environments and their interacting inhabitants

In viral entry by endocytosis

the host cell's cytoplasmic membrane engulfs the whole virion and pinches off, becoming a vesicle within the cell.

The MIC (minimum inhibitory concentration) is

the lowest concentration of an antimicrobial medication needed to prevent visible growth of a given bacterial strain in vitro.

HIV infection progresses to full-blown AIDS when

the number of CD4+ helper T cells in the patient's blood drops to a very low level.

Which of the following is NOT a concern/problem related to using phage therapy?

There is a limited number of different phages available for development in phage therapy, so this therapy has little potential for treating most bacterial diseases.

In order for viruses to enter host cells, they must bind to receptors on the host cytoplasmic membrane.

True

More than one mechanism of viral entry into a host cell exists.

True

Both enveloped and non-enveloped (naked) viruses can enter a cell by endocytosis.

True, Both enveloped and non-enveloped (naked) viruses can enter a cell by endocytosis.

Almost immediately upon entry, the viral nucleic acid alters the gene expression of the host cell.

True, The viral nucleic acid alters the gene expression of the host cell soon after infection.

Attachment of HIV to a host cell requires a receptor and co-receptor on the surface of the host cell.

True, receptor is CD4 t-cells and co-receptor is either CCR5 or CXCR4 (cytokine receptors.

Which of the statements about combination therapy is FALSE?

Using two medications is always twice as effective as using just one.

When AZT is present, which enzyme is inhibited?

Viral reverse transcriptase

viroids

-can infect plants -consist of RNA

Temperate phages are discarded when phages are being screened for therapeutic use. Why is this so?

-Temperate phages do not necessarily kill the bacterial host. -Temperate phages may cause bacteria to acquire new characteristics (lysogenic conversion).

Which of the following are advantages of phage therapy?

-There is an enormous number of phages on the planet, so finding possible candidates for therapeutics is relatively easy. -Because phages are so specific, there is less risk of dysbiosis in the patient.: *Dysbiosis*: An imbalance in the micro biome; often occurs with the use of antibiotics, particularly broad spectrum, because normal microbiota can be affected by the medication. -Phages replicate at the site of the bacterial infection.

What are the advantages of using commercial modifications of conventional susceptibility testing methods?

-They are less labor-intensive. -They can be automated, which improves speed and data analysis. -Results can be obtained in as few as 4 hours.

where are algae most likely to be found

-moist terrestrial habitats -surface of oceans, lakes and streams

Algae are

-single celled, photosynthetic eukaryotes -multicellular, phototsynthetic eukaryotes

Steps of the scientific process

1. make an observation about something and ask a question about the situation 2. develop an explanation and then devise and experiment to test this explanation 3. collect data from this experiment and draw a conclusion 4. communicating the methods, results, and conclusions

What is a bacteriophage?

A virus that infects and replicates inside a bacterial host.

Which of the medications mentioned is used to treat patients with HIV?

AZT, is used to treat HIV infection, because it inhibits the reverse transcriptase enzyme required for HIV replication.

Which step in the viral replication cycle would probably be the most efficient way to prevent viral infections?

Adsorption -Preventing viruses from adsorbing to host cells is the most efficient target because it prevents the host cell from actual infection. Also, vaccines that elicit antibody responses could protect for a lifetime.

In animal virus replication, an uncoating step is needed to release the nucleic acid from the capsid. Why is this step not needed in bacteriophage replication?

Bacteriophages inject their DNA into the host cell.

What do phage therapy and conventional antibiotic therapy have in common?

Both types of treatment have the potential to cause adverse side effects; While phage therapy is pretty safe, there is always the risk of endotoxic shock if it is used to treat a Gram-negative infection, as there would be with antibiotic treatment of a Gram-negative infection.

In order to bind to a host cell, the spikes of HIV have to attach to ______.

CD4 and a coreceptor -The virus must bind to a complex made of both CD4 and a coreceptor found on helper T-cells and macrophages.

Which of the following pathogens exhibit antibiotic resistance?

Clostridium difficile Staphylococcus aureus Pseudomonas aeruginosa Neisseria gonorrhoeae

because less than 1% of microorganisms can currently be grown in the laboratory, most of what we know about the other 99% comes from

DNA sequencing

Cells that lack compatible virus receptors are resistant to infection by that virus.

true

Individual viral particles have only one type of nucleic acid.

true

Retroviruses such as HIV have

two copies of single-stranded RNA

Removal of the capsid to release the virus nucleic acid into the host cytoplasm is called ______.

uncoating

What other ways do we have to fight viral infections?

vaccines -Antibiotics are NOT effective against viruses.

The HIV proviral DNA inserted into the host cell's DNA is used to make

viral mRNA which is used to make viral genome RNA. - HIV mRNA is made which directs host cells to make the HIV proteins, and multiple copies of genome RNA are synthesized which will be "wrapped" inside newly made capsids.