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Micro Exam 2

Terms in this set (66)

Contaminated hospital equipment represents a difficult environment to control harmful microbial growth. Regarding influences that affect disinfection of hospital equipment, which of the following is an accurate statement?

The cell wall of gram-negative bacteria is especially resistant to many chemicals that are used destroy microbes.
The presence of organic matter, such as dried blood or protein, will not affect the action of antimicrobial agents.
Biofilms, often found contaminating hospital equipment, are relatively simple targets for biocides to reach effectively.
Antimicrobial agents work best under reduced temperatures.
The cell wall of gram-negative bacteria is especially resistant to many chemicals that are used destroy microbes
Prior to drawing blood for a blood donation, the nurse will scrub the arm with a Betadine solution. This form of antimicrobial control would be called __________.

sanitization
disinfection
antisepsis
sterilization
antisepsis
Antisepsis is the destruction of vegetative pathogens on living tissue.
A disk-diffusion test using Staphylococcus gave the following results:

Disinfectant Zone of inhibition (mm)
A 0
B 2.5
C 10
D 5
In the table, which compound was the most effective against Staphylococcus?
C
The preservation of beef jerky from microbial growth relies on which method of microbial control?
desiccation
lyophilization
supercritical CO2
filtration
ionizing radiation
desiccation
Consider various effects of moist and dry heat to control microbial growth. Which of the following methods would best reduce microbes without altering the taste and chemical composition of beer?
pasteurization
autoclaving
hot-air sterilization
boiling
pasteurization

Correct. Pasteurization retains the properties of the alcohol and the protein structure. Although it does not destroy all microbes, it is adequate to destroy most of the harmful microbes while retaining flavor.
Which of the following physical methods of microbial control denatures proteins as a mechanism of action?
osmotic pressure
boiling or autoclaving
radiation
incineration
boiling or autoclaving

Correct. Heat denatures proteins by altering the tertiary structure, inhibiting their function.
Surface-active agents act by decreasing surface tension so that microbes can be more easily removed. All of the following agents use this mechanism of action EXCEPT __________.
soaps and detergents
acid-anionic sanitizers
halogens
quaternary ammonium compounds (quats)
halogens

Correct. This is the exception. The mechanism of action for halogens includes inhibiting proteins and acting as a strong oxidizing agent, but halogens do not act as surface-active agents.
Which of the following correctly lists, in increasing order, the resistance of microorganisms to chemical biocides?
gram-negative bacteria, fungi, protozoan cysts, mycobacteria
protozoan cysts, fungi, gram-negative bacteria, prions
gram-positive bacteria, fungi, endospores, prions
prions, gram-negative bacteria, vegetative protozoa, gram-positive bacteria
gram-positive bacteria, fungi, endospores, prions

Correct. Gram-positive bacteria are the easiest to destroy, and prions are the most difficult to destroy.
When microbial control methods are used, microbes are destroyed at a constant rate; there is no instantaneous death of all the microbes present. That microbial death rate is influenced by all of the following factors EXCEPT __________.

the time of exposure
the number of microbes
the microbial characteristics
toxins produced by the microbe
toxins produced by the microbe

Correct. Although microbial toxins may influence the status of an infection, these factors do not influence the death rate of the organism.
What are the products of semiconservative replication for a double-stranded DNA molecule?

Two double-stranded DNA molecules, one consisting of two parental strands and the other consisting of two daughter strands.
Two double-stranded DNA molecules, each consisting of one parental strand and one daughter strand.
One double-stranded DNA molecule, consisting of two daughter strands.
One double-stranded DNA molecule consisting of one parental strand and one daughter strand.
Two double-stranded DNA molecules, each consisting of one parental strand and one daughter strand
Why is DNA replication essential for a cell?


It allows the organism to repair any mistakes.
All organisms require two copies of DNA.
Because DNA is double-stranded.
An organism must copy its DNA to pass genetic information to its offspring.
An organism must copy its DNA to pass genetic information to its offspring.
What is the function of the parental DNA in replication?

It is passed into the offspring of the parent.
It serves as the template for DNA replication.
It gives the cell two complete copies of the DNA.
It allows for the DNA to be circular.
It serves as the template for DNA replication.
Which enzyme breaks the hydrogen bonds during replication?
Replication fork
DNA helicase
Stabilizing proteins
ATP
DNA helicase
How do stabilizing proteins work on the DNA?
They use ATP to break the hydrogen bonds.
They form the replication fork.
They bind to the single-stranded DNA.
They bind to the double-stranded DNA.
They bind to the single-stranded DNA.
Part C

In which direction does the replication fork move?

It moves ahead of the newly synthesized DNA.
It moves from the double-stranded DNA to the single-stranded DNA.
It moves towards the stabilizing proteins.
It moves ahead of the unzipped DNA.
It moves ahead of the newly synthesized DNA.
What ensures that the single strands of DNA do not come back together?

The replication fork
ATP
DNA helicase
Stabilizing proteins
Stabilizing proteins
Which of the following genetic elements is transcribed into a single mRNA?

The inducer
The repressor
The structural genes
The promoter
The operator
The structural genes
Which operons are always transcribed unless deactivated?

Inducible operons
Repressible operons
Inducible and repressible operons
Repressible operons
Which operons are never transcribed unless activated?
Inducible operons
Repressible operons
Inducible and repressible operons
Inducible operons
According to the animation, where on the DNA strand does a repressor bind?
The structural genes
The promoter
The operator
The inducer
The operator
What is the inducer molecule in the lac operon?

Glucose
Lactose
Galactose
Allolactose
Repressor proteins
Allolactose
With which genetic region does the repressor protein interact?

The operator region
lacZ
lacY
The regulatory gene
The promoter region
The operator region
When the cell is not in the presence of lactose,

transcription of the structural genes occurs.
no transcription of the regulatory genes occurs.
the repressor proteins bind to the operator.
the repressor proteins are inactivated.
the repressor proteins bind to the operator
What is the basic function of the lac operon?

To produce lactose when none is present
To produce glucose when none is available
To code for enzymes involved in synthesizing lactose.
To code for enzymes involved in catabolizing lactose.
To code for enzymes involved in catabolizing lactose.
According to the animation, to what genetic element does the RNA polymerase bind?
The repressor mRNA
The operator
The repressor protein
The promoter
The promoter
Why must primase be used before DNA polymerase when replicating DNA?

Primase stabilizes the single-stranded DNA.
Primase provides an RNA primer with a 3' end on which DNA polymerase can act.
Primase removes RNA primers, allowing DNA polymerase begin synthesis.
Primase unwinds the DNA double helix.
Primase provides an RNA primer with a 3' end on which DNA polymerase can act.
Which enzyme joins the gaps between synthesized DNA fragments of the lagging strand?

DNA ligase
Primase
RNAse
DNA polymerase
DNA ligase
What nucleotides would DNA polymerase add if it encountered the nucleotide sequence: ATTGC?

ATTGC
TAACG
CGTTA
GCAAT
TAACG
Which strand will require more RNA primers to complete synthesis?

The leading and lagging strands will require the same amount of RNA primers.
RNA primers are not required for DNA synthesis.
Leading strand
Lagging strand
Lagging strand
In which direction does DNA polymerase synthesize DNA for the lagging strand?

3' to 5'
5' to 3'
The lagging strand is not synthesized by DNA polymerase.
It alternates between strands (5' to 3', then 3' to 5').
5' to 3'
Gram-positive organisms with low G + C content are commonly called __________.

Firmicutes
Spirochaetes
proteobacteria
mycobacteria
Firmicutes
At 72 hours, the nurse reads Mr. Williams's PPD results and finds that they are negative. The febrile antibodies panel for Brucella spp. is positive, at a titer of 1:360. At 14 days, the blood cultures reveal the presence of gram-negative coccobacilli. The colonies appear smooth and slightly opaque. Initial biochemical reactions indicate that the organism is urease-, oxidase-, and catalase-positive, suggesting possible infection by Brucella spp. Because of the serology results and presumptive biochemical identification, the culture is sent to the state reference laboratory and the Centers for Disease Control and Prevention (CDC) for final confirmation.


Part C

Which of the following Brucella species is most likely indicated in this case?

Brucella abortus
Brucella suis
Brucella melitensis
Brucella canis
Brucella abortus
Using a mouse model, the investigator orally inoculates mice with a mutated strain of Brucella lacking the gene for production of urease. Indicate which of the following would LEAST support the hypothesis that urease plays a role as a virulence factor in establishing Brucella infection.

Mice infected with mutated Brucella will NOT demonstrate inhibition of phagosome acidification by ammonia.
Mutant and nonmutant strains will demonstrate the ability to transition through intestinal mucosa.
Counts of viable mutant strains from the upper gastrointestinal (GI) tract will be significantly less than those of nonmutant strains.
Mutant and nonmutant strains will demonstrate the ability to transition through intestinal mucosa.
Which of the following pathogenic characteristics would best allow Brucella organisms to produce a chronic infection in a host?

weakened inflammatory response
resistance to complement
resistance to antibiotics
sequestering of organism within the endoplasmic reticulum
sequestering of organism within the endoplasmic reticulum
Regarding the order Rhizobiales of the class Alphaproteobacteria, which genus includes human pathogens?

Agrobacterium
Brucella
Bradyrhizobium
Beijerinckia
Brucella
If a patient is diagnosed with a peptic ulcer, which genus of Proteobacteria is probably responsible?

Campylobacter
Myxococcus
Helicobacter
Desulfovibrio
Helicobacter
Which gammaproteobacteria are facultatively anaerobic, gram-negative rods that inhabit the intestinal tracts of humans and other animals?

Pseudomonadales
Legionellales
Vibrionales
Enterobacteriales
Enterobacteriales
For which of the following would growth on blood agar be a good diagnostic tool?

enterococci
all Gram-positive cocci
streptococci
staphylococci
streptococci
Which of the following characteristics are shared by Enterococcus and Streptococcus?

found on/in healthy carriers
cell arrangement
growth patterns on blood agar
none of the above
cell arrangement
Which of the following techniques would allow you to easily differentiate between Staphylococcus and Enterococcus?

genetic testing
Gram stain
simple stain
all of the above
all of the above
The term dermatophyte is typically used for fungi that cause which of the following?

systemic mycoses
subcutaneous mycoses
opportunistic infections
cutaneous mycoses
cutaneous mycoses
Select the eukaryotic organisms that are involved in causing or spreading disease.

Virus
Archaean
Helminth
Alga
Protozoan
Bacterium
Arthropod
Fungus
Helminth
Alga
Protozoan
Arthropod
Fungus
Select all of the statements below that accurately describe characteristics of algae.
Both asexual and sexual reproduction occurs among the diversity of algal species.

Algae may be green, red, or brown

Algae lack roots, stems, leaves, and vascular tissues that are found in terrestrial plants.

Some marine algae produce neurotoxins that can be concentrated in shellfish and pose a risk of paralytic shellfish poisoning to humans who consume the shellfish.

Most algae have a plantlike cell wall composed of cellulose.
Select the statements that correctly describe protozoa.
While living in the gut of their host, intestinal protozoan parasites are usually in the trophozoite form.

Most protozoa are motile via pseudopods, flagella, cilia, or undulating membranes.

Protozoan cysts enable protozoan parasites to survive during passage from one host to the next.

As a group, protozoa exhibit both asexual as well as sexual reproduction.
Select the statements that correctly describe medically important helminths.
Some helminth infections involve more than one intermediate host.

The major organ system apparent in tapeworm proglottids is the reproductive system.

Humans can serve as either definitive or intermediate hosts of flatworms.

Parasitic helminths lack a complete digestive system and they absorb nutrients directly through their cuticle.

Either eggs or larval stages of helminths may be infectious, depending on the species.
Which of the following organisms requires an additional nonhuman host to complete its life cycle?

Enterobius vermicularis
Ascaris lumbricoides
Necator americanus
Plasmodium species
Plasmodium species
Humans are the definitive host for __________, which is a type of __________.

Plasmodium; cestode
Echinococcus granulosus; tapeworm
Taenia solium; roundworm
Taenia saginata; tapeworm
Taenia saginata; tapeworm
Trichomonas vaginalis can be distinguished from other parasitic protozoa by which of the characteristics listed below?

It is a photosynthetic organism that lives in fresh water.
It has an undulating membrane, infects the vagina, and is frequently transmitted by sexual contact.
It is usually found in drinking water and is associated with fecal contamination.
It infects Anopheles mosquitoes and can be transmitted by a bite.
It has an undulating membrane, infects the vagina, and is frequently transmitted by sexual contact.
Which phylum of protozoa contains organisms that are nonmotile obligate intracellular parasites? (Hint: They cause a well-known tropical disease.)

Euglenozoa
ciliates
Apicomplexa
Amoebozoa
Apicomplexa

Apicomplexa contains many species that cause disease, including the Plasmodium species that cause Malaria.
How are viruses different from cells?

They do not contain genetic material.
They require a host in order to reproduce.
They do not contain enzymes.
They do not contain protein.
They require a host in order to reproduce.
What is the function of the structural elements of a virus?

To use all of the cell proteins
To package and protect the viral genome
To provide a source of energy for the virus
To package and protect the viral genome
Which of the following is true of viroids?

There are similarities between the base sequences of viroids and exons, resulting in the hypothesis that viroids evolved from exons.
Viroid is the term for a virus that infects plants.
Viroids are short pieces of naked RNA.
Viroids are typically extremely long and contain numerous genes.
Viroids are short pieces of naked RNA.

Correct. Viroids are infectious particles consisting of only a short piece of "naked" RNA (there is no capsid).
Which of the following statements regarding latent viral infections is true?

Latent infections can persist for years in an individual without causing any symptoms.
Latent viral infections are caused by the slow conversion of cellular glycoproteins from normal to infectious form.
Latent viral infections are almost always fatal.
During latent infections, small amounts of virus are produced, and virus numbers build up over time.
Latent infections can persist for years in an individual without causing any symptoms.

Viruses that exhibit latency can persist in a dormant state for years.
Lysogenic viral DNA integrating into the host genome is referred to as

a prophage.
lytic.
induction.
lysogeny.
a prophage.
Which of the following events might trigger induction of a temperate bacteriophage?

Normal cell division of an infected cell
An infected cell entering the logarithmic phase of growth
Exposure to UV light
Bacterial conjugation
Exposure to UV light
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

The host cell dies during the lytic stage.
The host cell is allowed to live during the lytic stage.
The viral DNA may integrate into the host genome during the lytic stage.
The host cell can only divide during the lytic stage.
The host cell dies during the lytic stage.
What is the fate of the prophage during the lysogenic stage?

It is copied every time the host DNA replicates.
It is packaged into viral proteins and maintained until the host is exposed to an environmental stress.
It is degraded by the activity of host defense enzymes.
It is released from the cell by lysing the cell.
It is copied every time the host DNA replicates.
Which of the following is true concerning a lysogenic viral replication cycle?

During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome.
During lysogeny, the viral DNA is present as a circular plasmid.
Once the lysogenic portion of the cycle has begun, virus is never produced again.
Lysogenic infections are similar to persistent infections, in that virus is constantly produced.
During lysogeny, the viral genome integrates into the host DNA, becoming a physical part of the chromosome
In which stage is the viral DNA introduced into the cell?

Assembly
Attachment
Penetration
Release
Biosynthesis
Penetration
In which stage does formation of mature viruses occur?
Biosynthesis
Penetration
Release
Assembly
Attachment
Assembly
The host DNA is usually degraded during which stage?

Penetration
Release
Attachment
Biosynthesis
Assembly
Biosynthesis
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?

The virus would not be able to infect new hosts.
The cell could still be revived by the virus.
The virus would infect new hosts.
The virus would not be able to infect new hosts
Part A

We sometimes are able to generate antibodies (immune system proteins) that bind to and cover up some of the proteins on the outermost portion of a virus while it is in the bloodstream. This renders the virus unable to reproduce. Which step of viral replication are antibodies directly preventing?

attachment
synthesis
assembly
uncoating
attachment
Enveloped viruses have a layer of lipids surrounding their capsid. This envelope is made mostly of host cell membrane. In which step does the virus acquire this envelope?

attachment
assembly
synthesis
release
release
Correct

During budding release, the virus "steals" some of the host membrane to use for itself.
What occurs during viral uncoating?

The viral proteins are synthesized.
The viral envelope is released.
The nucleic acid breaks apart, allowing for translation.
The capsid breaks apart, releasing the viral genome.
The capsid breaks apart, releasing the viral genome.
Which statement concerning viral structure is true?

Animal viruses usually contain a tail sheath and spikes.
Spikes are found on some viruses. They are very consistent in structure and can be used for identification.
All viruses contain an envelope, which is made of lipid, carbohydrate, and protein.
The proteins in the envelope are capsomeres.
Spikes are found on some viruses. They are very consistent in structure and can be used for identification
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