BIO CHAPTER 13

In strains of bacteria that are not resistant to beta-lactams, which part(s) of the bacterial cells are disrupted by the antibiotic?

the cell walls

Which changes in a bacterial cell might reduce the effectiveness of beta-lactam antibiotics?

the presence of enzymes that are able to break down the antibiotic

Which situation puts a healthy person at greater risk for a MRSA infection?

undergoing a medical procedure that weakens the immune system undergoing a procedure that causes a break in the skin being a child whose immune system is still maturing being elderly

Antibiotic-resistant bacteria have _____ fitness in the presence of antibiotics.

very high

fitness

The relative ability of an organism to survive and reproduce in a particular environment.

about how many are killed each year from MRSA

10,000

antibiotics

A chemical that can slow or stop the growth of bacteria; many antibiotics are produced by living organisms.

population

A group of organisms of the same species living together in the same geographic area.

binary fission

A type of asexual reproduction in which one parental cell divides into two.

stabilizing selection

A type of natural selection in which organisms near the middle of the phenotypic range of variation are favored by the environment.

diversifying selection

A type of natural selection in which organisms with phenotypes at both extremes of the phenotypic range are favored by the environment.

directional selection

A type of natural selection in which organisms with phenotypes at one end of a spectrum are favored by the environment.

Antibiotic-resistant strains of bacteria tend to first be found in hospitals. Which factor explains why this is the case?

Antibiotics are more likely to be present in hospitals, thus selecting for resistant strains.

How do bacteria resist the effect of antibiotics?

Bacteria produce by binary fission, acquiring new alleles may result in antibiotic resistance.

Which statement regarding drug-resistant bacteria is false? Antibiotic-resistant bacteria are more fit for an environment where antibiotics are used frequently. The ability to resist antibiotics may cause bacteria to be less fit in other environments where antibiotics are not present. Bacteria that are sensitive to antibiotics have a reproductive advantage in all environments. Bacteria with alleles for antibiotic resistance can pass that trait on to their offspring. The phenotype of a bacterium determines its fitness for an environment where antibiotics are present.

Bacteria that are sensitive to antibiotics have a reproductive advantage in all environments.

evolution

Change in allele frequencies in a population over time.

natural selection

Differential survival and reproduction of individuals in response to environmental pressure that leads to change in allele frequencies in a population over time.

A bacterial cell that is resistant to a particular antibiotic may spend a large amount of energy producing the modified proteins that are needed for resistance. In such a case, what would be the effect on this cell's fitness if no antibiotic was present?

Its fitness would be lower than other strains that lack resistance because it is spending energy that the resistant strains can use for other purposes, such as reproduction.

Which statement about evolution by natural selection is false?

Natural selection is a random change in allele frequencies over generations.

Which statement expresses the only way to prevent the evolution of new antibiotic-resistant bacteria?

Stop using antibiotics entirely.

gene transfer

The process by which bacteria can exchange segments of DNA between them.

adaptation

The process by which populations become better suited to their environment as a result of natural selection.

If you examine a natural population of bacteria, it is common to find some antibiotic-sensitive and some antibiotic-resistant strains, even if the population has never been exposed to any antibiotic. Which explanation could account for this situation?

The resistant strain developed as a mutation and had no negative effect on fitness.

An organism's fitness depends on its _____.

ability to survive and reproduce

The development and spread of a new gene for antibiotic-resistance in a population of bacteria that are exposed to that antibiotic would mean that trait is a(n) _____.

adaptation

Which factor is not going to affect how natural selection acts on a given group of organisms? reproductive success of individuals survival rate of individuals which phenotypes are present all of these none of these

all of these

Which factor may prevent most people from developing more than minor skin blemishes when they have a staph infection? Helpful bacteria on their skin keep staph in check. Their skin is a physical barrier that keeps out the bacteria. all of these Their immune systems are preventing the infection from spreading. They are practicing good hygiene, including frequent hand washing.

all of these

Which of these is NOT a pattern of natural selection? all of these none of these directional selection diversifying selection stabilizing selection

all of these

Which process has been shown to contribute to the evolution of antibiotic resistance in S. aureus? all of these gene swapping with other bacterial strains none of these overuse of antiviral medications genetic mutations during asexual reproduction

all of these

Why is the evolution of antibiotic resistance in bacteria happening so quickly? because bacteria can reproduce so quickly because any use of antibiotics will select for resistant bacteria because of overuse of antibiotics in livestock because of overuse of antibiotics in humans all of these

all of these

How do populations evolve, and what is there of evolution in antibiotic resistance?

an entire population can change when some traits are favored over others. Through fitness and natural selection. Populations evolve, not individuals. Antibiotic-resistance populations of bacterium emerge by directional selection in the presence of antibiotics.

Why aren't human populations evolving to produce immune systems that are able to fight off MRSA and other "superbugs"?

because the rate of human evolution is much slower than bacterial evolution

How do β-lactam antibiotics kill sensitive bacteria?

by destabilizing the cell wall

An individual who carries staph but isn't sick is referred to as _____.

colonized

A highly resistant antibiotic strain of S. aureus would reproduce _____.

equally in the presence or absence of antibiotic

Methicillin is currently used to treat staph infections.

false

A non-staph bacterium that is resistant to penicillin and a staph bacterium are found in the same host. After the bacteria grow and replicate, it is found that the staph bacteria is now penicillin resistant. This is likely due to _____ between the two bacteria.

gene transfer

Where is MRSA most likely to be a problem?

in the bloodstream

What is the evolutionary process called that causes antibiotic-resistant bacteria to increase and antibiotic-sensitive bacteria to decrease in an environment where antibiotics are present?

natural selection

All of these statements are true regarding S. aureus EXCEPT: it can be transmitted from person to person through used bar soap. all of these it can secrete toxic substances that can interfere with cellular functions. nearly 1% of the U.S. population is colonized with S. aureus. it can cause pimples, boils, and wound infections in otherwise healthy individuals.

nearly 1% of the U.S. population is colonized with S. aureus.

Which hypothetical antibiotic would treat bacterial infections by interfering with bacterial reproduction?

one that decreases cell membrane synthesis

What is staph, and can a person have it in the absence of an infection?

spherical bacterium that can cause pimples, boils, and wound infections. Yes more than 2% of people in the US carry and are disease free.

A bacterial cell with which modification might be resistant to antibiotics such as methicillin?

the ability to produce an enzyme that breaks down the antibiotic

Your physician had prescribed a β-lactam antibiotic for your sister. Your sister took biology in high school and is refusing to take the antibiotic because she says that it will affect osmosis in her cells. Which reason can you use to help your sister understand how the antibiotic will work?

β-lactam affects bacterial cell walls, and it can't affect human cells because they do not have cell walls.