Question

this chapter of the textbook includes a story about how hospitals are finding that populations of bacteria such as staphylococcus aureus are evolving resistance to more commonly used antibiotics such as methicillin, as well as to the antibiotics of \last resort,\ such as vancomycin. which of the statements below are correct about how bacteria evolve antibiotic resistance? correct answer(s)
bacteria acquire antibiotic resistance through gene flow; the antibiotic-resistance gene then increases in a population as the bacteria survive and reproduce.
evolution of antibiotic resistance can happen in even a single bacterium.
bacteria that happen to have mutations for antibiotic resistance are more likely to survive and reproduce.
if antibiotics are used, then bacteria will certainly evolve resistance to them.
antibiotics stimulate mutations that cause resistance in bacteria.

Explanation:

1. First statement: Gene flow (e.g., horizontal gene transfer) can spread resistance genes, and natural selection (survival/reproduction of resistant bacteria) increases their frequency. Correct.
2. Second statement: Evolution requires population - level change (change in allele frequencies over time), so a single bacterium can't evolve. Incorrect.
3. Third statement: Resistant bacteria survive antibiotics and reproduce more, increasing their numbers. This is natural selection. Correct.
4. Fourth statement: Antibiotics select for resistance, but resistance isn't guaranteed (depends on mutation availability, etc.). Incorrect.
5. Fifth statement: Mutations are random; antibiotics don't stimulate resistance - causing mutations, they select existing ones. Incorrect.

Answer:

• Bacteria acquire antibiotic resistance through gene flow; the antibiotic - resistance gene then increases in a population as the bacteria survive and reproduce.
• Bacteria that happen to have mutations for antibiotic resistance are more likely to survive and reproduce.