MICRO PEARSON EXAM 4

What are leukocidins?

Molecules that can degrade Ig

AMolecules that destroy the complement proteins

Molecules that are capable of destroying phagocytes

Molecules that are capable of destroying phagocytes

Measles viruses are capable of inactivating host defenses by

suppressing the immune system.

producing superantigens.

producing leukocidins.

destroying complement proteins.

suppressing the immune system.

Meningitis and gonorrhea are caused by

measles virus.

Pseudomonas species.

Neisseria species.

Neisseria species.

How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?

They cause the immune system to destroy IgA antibodies.

They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.

They cause fever, which destroys the complement proteins.

They cause the immune system to turn on itself.

They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.

How can capsules enable bacteria to evade the immune system?

A capsule is a superantigen that distracts the immune system.

Capsules can bind up IgA, rendering it inactive.

Capsules block the complement biding sites on the surface of the pathogen.

Capsules block the complement biding sites on the surface of the pathogen.

What is meant by selective toxicity?

Chemotherapeutic agents should act against the pathogen and not the host.

Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?

Humans and other animal hosts lack peptidoglycan cell walls.

Submit

Why is polymyxin only used on the skin?

It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.

Quinolones and fluoroquinolones act against what bacterial target?

DNA gyrase

Why is it difficult to find good chemotherapeutic agents against viruses?

Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.

Submit

Which bacterium contains a large Ti plasmid and causes crown gall disease in plants?

Agrobacterium tumefaciens

Which of the following features of Salmonella prevent it from being phagocytosed?

Flagella

Where do Salmonella pathogens grow and replicate in the infected host?

Inside phagocytes

Where is the site of Shigella attachment in the host?

M cells

How do Shigella cells move between host cells?

They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.

What is the etiologic agent of typhoid?

Salmonella

Widespread antimicrobial drug resistance is usually passed by

horizontal gene transfer.

The decrease or loss of virulence of a pathogen is referred to as

attenuation.

Microbes that have a mutualistic relationship with their host are beneficial to their host, while __________.

commensals have little or no effect on the host

symbionts benefit at the expense of the host

parasites cause disease

pathogens kill the host

commensals have little or no effect on the host

An organism living in the bottommost region of a body of water is described as being

litoral.

pelagic.

neritic.

benthic.

benthic.

Endotoxins are also known as

Lipid A.

interleukin-1.

prostaglandins.

cytokines.

Lipid A.

When would endotoxins be released from a bacterial cell?

When the cell dies

During bacterial conjugation

When the cell moves toward a energy source

When the cell attaches to a host cell in the human body

When the cell dies

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

Pain

Nausea

Weakness

Fever

Fever

Submit

Why is a release of endotoxin into the bloodstream potentially deadly?

It can lower blood pressure and cause the patient to go into shock.

It results in dehydration of the patient.

Endotoxin can quickly enter the brain from the bloodstream, causing brain damage.

It causes necrosis of the liver.

It can lower blood pressure and cause the patient to go into shock.

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)

enterotoxin.

A-B toxin.

neurotoxin.

superantigen.

cytotoxin.

cytotoxin.

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

A-B toxins do not bind to cell surfaces.

Both the A and B domains have the ability to bind to cell surface receptors.

B domain

A domain

B domain

How are superantigens different from other types of exotoxins?

Superantigens only act against host neurons.

Superantigens cause an overstimulation of the host immune system.

Superantigens must be endocytosed into a target cell before becoming active.

Superantigens are comprised of two functional domains.

Superantigens cause an overstimulation of the host immune system.

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)

cytotoxin.

membrane disrupting toxin.

superantigen.

enterotoxin.

superantigen.

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)

superantigen.

membrane disrupting toxin.

neurotoxin.

enterotoxin.

neurotoxin.

Pathogenicity is the ability

of the pathogen to inflict damage on the host.

of the host to resist damage by the pathogen.

of the host to inflict damage on the pathogen.

None of these are correct.

of the pathogen to inflict damage on the host.

Oxygen depleted zones at varying depths in marine waters between 100-1000m are called __________.

photic zone

oxygen minimum zones

dead zones

pelagic zones

oxygen minimum zones

Which of the following is NOT a subunit of lipopolysaccharide (LPS)?

lipid A

M protein

core polysaccharide

O-specific polysaccharide

M protein

A population consists of

all of the individuals that interact in different areas.

all of the individuals of all species in the same area.

all of the individuals of one species in the same area.

all of the individuals that interact in the same area.

all of the individuals of one species in the same area.

Which of the following is an important virulence factor for dental caries?

pili

siderophores

endotoxin

polysaccharide adhesion

polysaccharide adhesion

Which of the following is NOT important for the adherence of bacteria to host tissues?

capsule

lipopolysaccharides

slime layer

adhesins

lipopolysaccharides

All of the following are true of biofilms EXCEPT that __________.

biofilms protect organisms from antibiotics

biofilms are composed of only one species at a time

biofilms form on virtually all submerged surfaces in nature

biofilm formation and dispersal are regulated processes

biofilms are composed of only one species at a time

All AB toxins have which of the following?

two subunits

hemolytic activity

immunogenic properties

lipid A

two subunits

Many microbial habitats are unsuitable for plants and animals.

True

False

True

Penicillin and other β-lactam antibiotics inhibit cell-wall synthesis. What makes them effective at killing bacterial cells?

Bacteria may burst or desiccate when their cell wall is weakened by the action of these antibiotics.

Bacteria are generally hypertonic relative to their environment, so they desiccate when their cell wall is weakened by the action of these antibiotics.

Bacteria are generally hypertonic relative to their environment, so they burst when their cell wall is weakened by the action of these antibiotics.

Bacteria are generally hypotonic relative to their environment, so they burst when their cell wall is weakened by the action of these antibiotics.

Bacteria are generally hypertonic relative to their environment, so they burst when their cell wall is weakened by the action of these antibiotics.

The collective term for the organisms living on or in the human body, as opposed to a general term for organisms in an environmental habitat, is

the microbiota.

transient microbial flora.

pathogens.

the human microbiome.

the human microbiome.

Staphylococcus aureus and Streptococcus pyogenes strains can produce ________ that cause(s) the severe and sometimes life-threatening symptoms of toxic shock syndrome.

endotoxin

superantigen toxins

AB toxins

cytolytic

superantigen toxins

Archaea and Bacteria dominate the upper 100 m of the open ocean while viruses dominate depths greater than 100 m.

True

False

False

An outer coat consisting of a dense, well-defined polymer layer surrounding a cell and used in attachment is called a

capsule.

cytoplasmic membrane.

lipopolysaccharide layer.

pilus.

capsule.

Exotoxins are ________, but endotoxins are ________.

lipopolysaccharide-lipoprotein

complexes / proteins

lipids / proteins

carbohydrates / proteins

proteins / lipopolysaccharide-lipoprotein complexes

proteins / lipopolysaccharide-lipoprotein complexes

Which of the following is the mechanism of action of aminoglycoside antibiotics?

Prevention of peptidoglycan crosslinking

Inhibition of cell wall biosynthesis

Targeting the 30S ribosomal subunit

Inhibition of DNA replication

Targeting the 30S ribosomal subunit

Which of the following is an example of a biofilm?

dental plaque

transient skin microbes

marine diatoms

a planktonic microcolony

dental plaque

The best term to describe the general process by which microorganisms cause diseases is known as

virulence.

pathogenesis.

invasion.

infection.

pathogenesis.

A mechanism for penicillin resistance in bacteria is

splitting the β-lactam ring of the antibiotic.

acetylation of the antibiotic.

phosphorylation of the antibiotic.

confirmation change of the antibiotic.

splitting the β-lactam ring of the antibiotic.

The rhizosphere is __________.

the soil immediately surrounding the root of a plant

the surface of the roots of a plant

all of the microorganisms living in soil

the top inch of soil that contains a large number of microorganisms

the soil immediately surrounding the root of a plant

The first antibiotic to be characterized was a

quinolone.

cephalosporin.

β-lactam.

macrolide.

β-lactam.

Factors that enhance an organism's ability to adhere to host tissues include __________.

lipopolysaccharide

fimbriae

adherence enzymes

peptidoglycan

fimbriae

A small farm pond containing many species of microorganisms (bacteria, cyanobacteria, algae, and protozoa) was perturbed when runoff from a manure pile entered the pond. The added nutrients soon turned the water green due to a bloom of cyanobacteria. How did this affect the microbial community in the pond?

Species richness decreased and species abundance decreased.

Species richness decreased and species abundance increased.

Species richness increased and species abundance decreased.

Species richness increased and species abundance increased.

Species richness decreased and species abundance increased.

What is meant when a bacterium is said to become "resistant" to an antibiotic?

The antibiotic kills or inhibits the bacterium.

The antibiotic is metabolized by the bacterium, providing more energy for growth of the cell.

The bacterium is neither killed nor inhibited by the antibiotic.

The antibiotic mutates in a way that benefits the bacterium.

The bacterium is neither killed nor inhibited by the antibiotic.

When a patient is treated with antibiotics, __________.

mutations occur in all of the bacterial cells

sensitive bacterial cells multiply uncontrollably

the drug will kill or inhibit the growth of all of the sensitive bacterial cells

the drug will kill or inhibit the growth of all of the resistant bacterial cells

mutations will occur in the sensitive bacterial cells, but not in the resistant bacterial cells

the drug will kill or inhibit the growth of all of the sensitive bacterial cells

The process of acquiring antibiotic resistance by means of bacteriophage activity is called

transduction.

R-plasmid acquisition.

point mutation.

transformation.

transduction.

Which of the following mutations would not result in antibiotic resistance?

Missense mutation

Nonsense mutation

Silent mutation

Frameshift insertion

Frameshift deletion

Silent mutation

R-plasmids are most likely acquired via

translation.

transformation.

bacterial conjugation.

transduction.

bacterial conjugation.

Certain traits that allow pathogens to create infection and cause disease are termed

streptokinases.

hyaluronidases.

collagenases.

virulence factors.

virulence factors.

Which of the following enzymes breaks down the "glue" that holds cells together?

Fibrinolysin

Streptokinase

Hyaluronidase

Collagenase

Hyaluronidase

Which of the following virulence factors would be found in Staphylococcus aureus?

Collagenase

Hyaluronidase

Streptokinase

Staphylokinase

Staphylokinase

How do fibrinolysins enhance a pathogen's virulence?

They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.

They destroy the fibers that are found at the base of superficial tissues, allowing for deeper penetration by the pathogen.

They destroy the molecules that hold cells together.

They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.

Invasion is the ability of a pathogen to enter into host cells or tissues, spread, and cause disease.

True

False

True

Which antibiotic is overcome by beta-lactamases?

Tetracycline

Sulfonamide

Penicillin

Tetracycline, Penicillin, and Sulfonamide are all affected by beta-lactamase.

Penicillin

How might efflux pumps increase antibiotic resistance in bacteria?

Resistant bacteria may have a greater number of efflux pumps on their cell surfaces.

Some bacteria can decrease the specificity of their efflux pumps, increasing the number of different antibiotics the pumps can eliminate.

Some bacteria can change the chemical structure of the antibiotic.

Efflux pumps can never be modified to increase antibiotic resistance.

Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.

Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.

Bacteria that are resistant to sulfonamide have enzymes that have a greater affinity for what?

PABA

Sulfonamide

Tetrahyrdrofolic acid

Tetracycline

PABA

Why would an efflux pump for penicillin located on a bacterial cell membrane not be effective at providing resistance to the drug?

The efflux pumps would not stop penicillin from blocking metabolic pathways.

There are fewer efflux pumps on the cell membrane.

The cell membrane is the target of penicillin.

Penicillin disrupts the cell wall, which is located outside of the cell membrane.

Penicillin disrupts the cell wall, which is located outside of the cell membrane.

Membrane transport proteins are required for which mode(s) of antibiotic resistance?

Modification of a porins

Efflux pumps

Efflux pumps, beta-lactamases, and modification of porins all utilize membrane transport proteins.

Modification of a metabolic enzyme

Beta-lactamases

Efflux pumps, beta-lactamases, and modification of porins all utilize membrane transport proteins.

Due to a vast array of nutrients, microorganisms are often capable of sustaining exponential growth in the environment.

True

False

False

A researcher wanted to determine the LD50 (lethal dose that kills 50% of the infected hosts) for a newly isolated bacterial pathogen. Mice were inoculated with diluted cultures containing between 101 and 107 cells. After two days, all of the mice had died EXCEPT for the uninoculated controls. Which of the following is the most likely explanation?

This pathogen is highly virulent in mice.

Mice are not good model animals for this pathogen.

The pathogen has become attenuated.

The pathogen has a very high LD50.

This pathogen is highly virulent in mice.

Endotoxins are comparatively different from exotoxins, because __________.

endotoxins are not secreted proteins

exotoxins can affect sites distant from the infection site

endotoxins are associated with more fatalities

All the listed responses are correct.

All the listed responses are correct.