Microbiology Midterm Review

Virus X can infect rodents and birds, whereas Virus Y infects humans. Which has a broader host range?

Virus X

This nutrient is a major part of all organic compounds in the cell as well as water, the major component of the cell

Oxygen

A naked virus fuses with the host cell membrane.

False

All viruses leave a cell by exocytosis.

False

Animal viruses always kill cells they infect.

False

Both human and bacterial cells divide by mitosis.

False

T-even phages can replicate independently of a host cell.

False

True or false: The causative agent could be cultured from a patient's stool specimen and Gram-stained to determine its specific identity.

False

True or false: The patient in the opening case file was diagnosed with viral meningitis and would be treated with antibiotic drugs to clear the infection.

False

True or false: The patients in the opening case file were diagnosed with viral gastroenteritis and were treated with antibiotic drugs to clear the infection.

False

True or false: Viruses belong to the Domain Archaea.

False

Viruses can be grown on culture media like bacteria.

False

What factors can affect the doubling time of a bacterial cell?

Temperature, Moisture, pH, Oxygen levels, - All of these factors can affect growth rates.

A spectrophotometer is used to measure the light scattering properties of a bacterial culture. As the number of bacteria increase, more light is scattered and less is transmitted to the detector

Turbidometry

During binary fission, one bacterial cell becomes _______ cells.

Two genetically identical

You ingest 20 cells of Salmonella. This bacterium has a doubling time of 30 minutes. After 4 hours, how many of these bacteria would be present in the body (assuming no immune system responses or other biological activities affect its growth)?

5,120

This entire cycle can range from __ hours to __ hours in some viruses.

8; 36

Nitrogen is essential for the formation of proteins, nucleic acids, and the source of cellular energy, ____. The main reservoir of earth's nitrogen is in the form of ____, which is unavailable for cellular use. A few species of bacteria can carry out ____ which converts gaseous nitrogen into a usable form. As with carbon, heterotrophs must obtain their nitrogen from the organic molecules of other organisms.

ATP; N₂ gas; nitrogen fixation

If you could design a drug to "hide" or block sialic acid on respiratory cells, what stage of the life cycle of influenza would be directly impacted?

Adsorption

Order these steps of the lytic cycle. A. Assembly B. Penetration C. Lysis D. Synthesis E. Adsorption

Adsorption, Penetration, Synthesis, Assembly, Lysis

Describes an organism that does not use oxygen, but can grow to a limited extent in the presence of oxygen

Aerotolerant anaerobe

In chapter 5, you learned that viruses can be classified into families. Norwalk virus belongs to which family of viruses?

Caliciviridae, RNA viruses

Gram staining of the patient's samples would help to identify which type of pathogens?

Bacteria

How does lysogeny affect humans?

Bacteria can become virulent due to phage genes, causing greater damage to infected human host.

____ is the acronym used to describe the list of essential nutrients required by all organisms for survival. ____ differ from ____ in how they obtain their source of carbon; heterotrophs must rely on other organisms to provide them with organic molecules such as proteins and nucleic acids, whereas autotrophs are able to "fix" carbon from ____, making them nutritionally independent.

CHONPS; heterotrophs; autotrophs; inorganic CO₂

Which of the following is NOT a transmission method for Norwalk virus?

Biological vectors

If you wanted to cultivate the infectious agent in Natasha's case, what medium would you choose to grow the agent?

Bird embryos or cell culture

A fundamental component of organic molecules consumed by and produced by the cell

Carbon

Uses simple inorganic compounds for energy and carbon dioxide for a carbon source (example: methanogens)

Chemoautotroph

Converts nutrients from other organisms into energy and uses an organic carbon source (example: protozoa)

Chemoheterotroph

An automated cell-counting device that scans a culture as it passes through a tiny pipette

Coulter counter

This method uses a special slide (cytometer) and cells are counted by observing them through a microscope

Direct cell count

The T-even bacteriophages such as T2 and T4 infect ________.

Escherichia coli

An automated cell-counting device that requires fluorescent labeling of cells that will be scanned and counted

Flow cytometry

Why are CD4 counts related to HIV infection?

HIV can only bind to cells with CD4 receptors.

Some viruses may also possess an external membraneous covering that comes from the _____.

Host cell

How does bacteriophage DNA get into the host cell?

It is injected

Describes an organism that is unable to use oxygen and lacks the enzymes to detoxify oxygen, thus requiring the absence of oxygen for growth

Obligate anaerobe

You leave your potato salad out on the table at the company picnic. When you made it, you unknowingly introduced 100 cells of Salmonella. How much time will it take for the population of Salmonella to reach at least one million if its doubling time is 20 minutes at picnic conditions?

Over 4 hours

The activation of a prophage to enter the lytic cycle is called ______.

induction

Utilizes the tissues of a live host and an organic carbon source (example: pathogens)

Parasite

____, essential for the formation of membranes, nucleic acids, and ATP, as well as sulfur, necessary for certain amino acids, must be harnessed from mineral deposits in rocks and oceans.

Phosphorus

Uses sunlight as an energy source and carbon dioxide as a carbon source (example: cyanobacteria)

Photoautotroph

Uses sunlight as an energy source and an organic carbon source (example: purple photosynthetic bacteria)

Photoheterotroph

When present, what is the viral envelope composed of?

Proteins and lipids

What type of bacteria will grow in the refrigerator, and why is this usually not a concern?

Psychrophiles; very few are pathogenic to humans

An envelope is acquired during which step of the viral life cycle?

Release

Metabolizes organic matter of dead organisms for energy and uses an organic carbon source (example: fungi)

Saprobe

A cell's proteins are misshapen or unstable because of its lack of the amino acids cysteine and methionine (composed in part by this nutrient)

Sulfur

A bacteriophage initially associates with which bacterial structure?

The bacterial cell wall

How are temperate phages replicated?

The phage is replicated along with the host cell's genome.

What will happen once a virus has entered a host cell and uncoated?

The synthesis of new virions will occur

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

True

Bacteriophage DNA directs the degradation of the bacterial host cell's DNA.

True

Both enveloped and naked viruses can enter a cell by endocytosis.

True

Both lytic and lysogenic cycles eventually lead to bacterial host cell damage.

True

Environmental factors control microbial growth through their influence on enzyme activity.

True

The capsid of a virus is ________.

a protein shell that surrounds the nucleic acid

The general steps in viral replication (in order) are ________.

adsorption, penetration, synthesis, assembly, release

The general phases in the life cycle of animal viruses are ____, ____, ____, ____, ____, and ____.

adsorption, penetration, uncoating, synthesis, assembly, release

Viral spikes ________.

attach specifically to host cell receptors

Rabies virus has a _______ host range as compared to hepatitis B virus.

broad

All viruses are composed of a ____ made of ____ which surrounds the inner core containing ____ or RNA.

capsid; protein; DNA

Nutrient depletion and waste accumulation prevent cell growth and cells die exponentially

death phase

Every virus particle contains ________.

either DNA or RNA

These viruses are known as _____, whereas viruses without this outer covering are called _____ viruses.

enveloped; naked

Phase during which cells are growing very quickly, at their maximum rate of cell division

exponential growth phase

Describes an organism that can grow in the presence of oxygen and can detoxify it, but can also grow in the absence of oxygen

facultative anaerobe

A cell requires this nutrient for pH maintenance and the bonds between DNA strands

hydrogen

Refrigeration will _____ the doubling time of most pathogens.

increase

Adjustment period during which cells are dividing slowly while they adjust to growth conditions

lag phase

The final step in T2 bacteriophage infection results in _______.

lysis of the bacterial cell and release of new viral particles

Viral cycles that end in release of the new phages and immediate destruction of the host bacterial cell are referred to as ______.

lytic

Most of the microbiota in the human body are classified as ______.

mesophiles

Describes an organism that cannot grow at normal atmospheric oxygen concentrations, but does require a small amount of oxygen for growth

microaerophile

Once inside the host cell, viral DNA directs production of _______.

new viral particles

A cell is unable to synthesize proteins and nucleic acids due to a deficiency in this essential nutrient required for their structure

nitrogen

Regardless of an organism's ability to reside in seemingly inhospitable conditions, all cells require certain ____ for survival. How they obtain those nutrients varies from organism to organism, and there is no greater versatility than the ability of ____ to harness chemicals from a variety of sources.

nutrients; bacteria

Describes an organism that requires oxygen for growth and has the enzymes to remove toxic by-products of oxygen metabolism

obligate aerobe

A major difference in the replication of animal viruses and bacteriophages is the ______ step.

penetration

An infection in animals similar to a lysogeny in bacteria is called a(n) ______ infection.

persistent

A cell is unable to produce ATP and its cell membrane has lost its integrity because of a deficiency of this nutrient

phosphate

Viral capsids are composed of ________.

protein

Phage DNA encodes for the proteins of the viral capsid and ________.

regulatory proteins which direct the production and assembly of the capsid proteins

Cells must ________ their DNA prior to cell division.

replicate

Pathogens usually have _____ doubling times.

short

In general, viruses are ______ than bacterial or protozoan pathogens and are most often measured in units called ________.

smaller; nanometers

In general, viruses are ________ than bacterial or protozoan pathogens and are most often measured in units called ________.

smaller; nanometers

Enveloped viruses use glycoproteins called _______ to specifically bind with their host cells.

spikes

Phase during which nutrient depletion and accumulation of wastes begin to slow cell growth such that the rate of cell increase equals the rate of cell death

stationary growth phase

In viral entry by endocytosis ________.

the host cell's plasma membrane surrounds the whole virion and forms a vesicle