Fundamentals Biology Chapter 13

In the presence of penicillin... What happens to a penicillin-sensitive strain of S.aureus? What happens to a penicillin-resistant strain of S.aureus?

A sensitive strain of S. aureus will eventually burst (lyse) and die because of its weakened cell wall. A resistant strain of S. aureus will not be affected by penicillin and will continue to grow.

Examples of population.

All the prairie dogs in a prairie dog town, all the bees in a hive, and all the pigeons in new york city.

Binary fission is asexual. What does that mean? How could two daughter cells end up with different genomes at the end of one round of binary fission?

Asexual reproduction involves only one parent. That parent passes on a copy of all of its genetic material to its offspring. This means that the offspring are copies of the parent. The two daughter cells that are the products of binary fission could be genetically different if a mutation occurred during replication of the parent genome before division. One copy of the genome would contain the mutation and one copy would not, and each daughter cell would inherit one of the two different copies.

What is the difference between S. aureus colonization and S. aureus infection?

In colonization, the bacteria are growing on or in the body without causing disease. Infections are associated with disease.

If we take the fittest bacterium from one environment—one in which the antibiotic amoxicillin is abundant, for example—and place it in an environment in which a different antibiotic is abundant, will it retain its high degree of fitness?

Not necessarily; fitness depends on the ability of an organism to survive and reproduce, and it may not do this as well in a different environment.

The term ''MRSA'' as it is used today refers to?

S. aureus bacteria that are resistant to many antibiotics

In humans, very-large-birth-weight babies and very tiny babies do not survive as well as mid-range babies. What kind of selection is acting on human birth weight?

Stabilizing selection

Can S. aureus be present in or on a person who has no evidence of an infection?

Yes; S aureus is a common skin bacterium.

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 a single parental cell simply replicates its single chromosome, grows, and then splits into two daughter cells, each with own copy of the parental DNA. Is a chance that mutation will occur.

stabilizing selection

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

directional selection

a type of natural selection in which organisms with phenotype at one end of a spectrum 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

MRSA infection is caused by...

bacterium Staphylococcus aureus-often called simply ''staph''.

How do beta-lactam antibiotics kill sensitive bacteria?

by destabilizing the cell wall

Evolution

change in allele frequencies in a population over time

A sensitive S.aureus bacterium acquires a new gene that allows it to resist the effects of beta-lactam antibiotics (that is, the bacterium is now resistant). What might the protein encoded do?

digest beta-lac-tam antibiotics.

The evolution of antibiotic resistance is an example of?

directional selection.

What are the two major mechanisms by which bacterial populations acquire genetic diversity?

gene transfer and mutation.

MRSA is most likely to be problematic if found...

in the bloodstream.

What is the evolutionary term of the term ''fitness''?

reproductive success. How well an organisms adapts to its environment and reproduces.

Staphylococcus aureus is shaped as what?

spherical bacterium that can cause pimples, boils, and wound infections. S. aureus can be passed from person to person by direct contact with contaminated skin or by transfer of the bacteria via contaminated objects or surfaces.

natural selection

the greater survival and reproduction of individuals with certain traits in a particular environment that leads to a change in allele frequencies in a population over time.

What is the environmental pressure in the case of antibiotic resistance?

the presence or absence of antibiotics in the environment.

Gene transfer

the process by which bacteria can exchange segments of DNA between them. In which pieces of DNA pass from one type of bacteria to another.

Adaptation

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

Fitness

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