Microbiology Lab 4

Which of the following characteristic(s) describe(s) viruses? Select all that apply.

1. They contain DNA or RNA

2. They aren’t composed of cells

3. They exhibit metabolism while outside of the host cell

4. They are considered non-living

1, 2, 4

Which domain of life do viruses belong to?

They don’t belong to a domain.

Which of the following characteristics describe viruses?

They are filterable.

True or false? Viruses obtain their envelope by encapsulating themselves with the host cell’s plasma membrane as they exit the cell. *

True

What type of microscopy must be used to visualize most viruses? *

Electron microscopy

True or false? In general, when comparing sizes of viruses, prokaryotes, and eukaryotes, prokaryotes are the smallest.

False

What viral shape does the ebolavirus have? *

Helical

What viral shape does the smallpox virus have?

Complex ovoid

What viral shape does the bacteriophage have?

Complex

What viral shape does the adenovirus have?

Icosahedral

Identify the viral capsid structure shape labeled “A”.

Helical

Identify the viral capsid structure shape labeled “B”.

Icosahedral

Identify the viral capsid structure shape labeled “C”.

Complex

Which type of pathogen possess peplomers?

Virus

A polyhedral virus that has 20 triangular-shaped sides are called ____ viruses.

Icosahedral

“Naked” viruses lack what structural component?

Envelope

Viruses are surrounded by a protein capsid composed of individual subunits called

Capsomeres

True or false? For a spiked virus to infect a host cell, the cell must possess a specific receptor that is recognized by the viral spikes.

True

True or false? Mutations in the sequence that codes for viral spike proteins are never beneficial to the virus.

False

Which of the following is NOT a characteristic used to classify viruses?

Cell wall composition

Which structure of viral nucleic acid is used directly as mRNA that is translated using the host cell’s machinery and molecules?

ssRNA+

HIV is a retrovirus. What viral enzyme is used to produce a dsDNA copy of its ssRNA+ genome?

Reverse transcriptase

A ____ is an infectious viral particle that has yet to infect its host’s cells.

Virion

What is the host cell receptor located on lung and heart cells that SARS-CoV-2 viral spikes recognize?

ACE-2

Why are RNA viruses that use RNA-dependent RNA polymerase for transcription more likely to have genome mutations?

The enzyme doesn’t have proofreading capabilities.

Antigenic ____ occurs when advantageous mutations in viral genomes result in minor changes.

Drift

Antigenic ____ occurs when there is a reassortment of genetic material from coinfecting viruses that produce a new viral strain.

Shift

Which of the following is NOT a disease caused by prions?

Lou Gehrig’s disease

Prions are ____.

Misfolded proteins

Prions that cause mad cow disease are transmitted to humans by

Consuming contaminated beef

True or false? A naked virus injects its nucleic acid into the host cell.

True

Which nucleic acid type of virus uses its genetic material directly as mRNA?

ssRNA+

How do naked viruses generally exit the host cell?

By lysing the host cell.

The presence of specific ____ on viruses determine whether it can infect a particular cell or not.

Receptor

The first human virus was discovered in 1901. What scientist discovered the first human virus?

Walter Reed

Some scientists theorize that's an ancient virus infected a bacterium, helping it produce the first cell ___.

Nucleus

The prefix “corona-” means “crown”. What structure makes coronaviruses look “crowned”?

Spikes

What diagnostic tool is used to detect certain genetic markers of SARS-CoV-2?

Reverse transcriptase PCR

A serological test (blood test) for COVID-19 assess if a person has ____ to the virus in their blood.

Antibodies

Who was awarded the Nobel prize in 1997 for discovering the fact that prions caused scrapie in 1982?

Stanley Prusiner

How do prions produce more infectious proteins?

The misfolded prion protein converts a correctly folded protein.

What is the name of the human prion disease that is caused by eating prion contaminated beef?

Variant CJD

What is the name of the human prion disease that is caused by a single mutation in the gene that codes for the prion protein?

Gerstmann-Straussler-Scheinker syndrome

A significant increase in what secondary protein structure makes infectious prion protein protease resistance?

Beta sheets

What abbreviation represents the infectious prion protein?

PrP^SC

The red arrows are pointing to

Single bacterial colonies

True or false? A single colony of bacteria contains genetically diverse bacteria.

False

What is the primary purpose of the isolation streak technique?

To obtain isolated colonies of bacteria.

True or false? The two main types of isolation streak methods are the quadrant streak and the z-streak.

False

In which real-life circumstance might a microbiologist perform an isolation streak? Select all that apply.

1. To determine whether an infection contains more than one type of bacterium.

2. To detect contamination in a laboratory culture.

3. To isolate the causative agent of the disease.

4. To create a lawn of bacteria for antibiotic sensitivity testing.

1, 2, 3

Which scene illustrates the correct way to label a plate? Note: the difference between scene 1 and scene 2 is that scene 1 labeling occurs on the bottom of the plate and scene 2 labeling occurs on the lid of the plate. *

Scene 1

True or false? This image depicts a successful isolation streak.

True

Which is the lowest-numbered sector that contains well-separated isolated colonies?

Sector 3

How many different colony types do you see on the streak plate? *

2

Your lab partner asks you about their streak plate that was streaked and incubated, but no growth is visible. You respond that the lack of growth could have resulted from forgetting to… Select all that apply. *

1. Drag inoculum from the first sector into the second sector

2. Cool the loop before dipping it in the specimen

3. Obtain inoculum from the specimen tube

4. Sterilize the loop before dipping it into the specimen

2, 3

You perform an isolation streak from pond scum taken from a local farm. After an overnight incubation, you observe the plate. The bacterial colonies are similar in shape, but they differ in color; some are yellow, some are red, and some are fluorescent green. What conclusions, if any, can you determine from these results?

The sample appears to contain at least three different kinds of bacteria.

Which of the following is the most likely explanation for what you see on the isolation streak plate?

The streak was not extended from the second sector to the third.

Which of the following is the most likely explanation for what you see on the isolation streak plate?

The loop was not sterilized between sectors.

Which of the following is the most likely explanation for what you see on the isolation streak plate?

Each previous sector was reentered too many times when streaking into the next one.

Which of the following is the most likely explanation for what you see on the isolation streak plate?

The loop was dipped back into the tube to inoculate each sector.

When streaking a sector when performing an isolation streak, you want the cells to “thin out” along the streak. Which of these practices will increase your chances of getting isolated colonies at the end of streaking?

Make sure not to cross into the neighboring sector after the initial drag through.