Question 1

Which of the following best describes the relationship between Buchnera aphidicola and aphids?

Accepted Answer

Obligate mutualism, where both partners benefit and cannot survive without each other.

Question 2

What is the primary function of Buchnera aphidicola in aphids?

Accepted Answer

Synthesizing tryptophan (Trp) for the aphid, which the aphid cannot produce itself.

Question 3

Based on the table showing the effect of chlortetracycline on aphids, what can be inferred about the role of Buchnera in aphid development?

Accepted Answer

Buchnera is essential for normal aphid growth and reproduction, as antibiotic treatment reduces viable offspring to zero.

Question 4

Which of the following best explains why the Buchnera genome is much smaller than that of E. coli?

Accepted Answer

Buchnera has lost many genes over millions of years of co-evolution with aphids, relying on the host for essential functions.

Question 5

In the trp operon, what happens when tryptophan levels are low?

Accepted Answer

Transcription of the entire trp operon occurs, allowing synthesis of tryptophan.

Question 6

Which stem-loop structure in the trp operon attenuation mechanism allows transcription to continue?

Accepted Answer

Pairing of Region 2 with Region 3 forms a nonterminating stem loop.

Question 7

If an aphid is raised in a germ-free environment and fed a diet supplemented with amino acids, what is the expected outcome?

Accepted Answer

The aphid will grow normally, as the supplemented diet compensates for the absence of Buchnera.

Question 8

Which of the following is a key difference between mutualism and cooperation in microbial interactions?

Accepted Answer

Mutualism is obligatory for both partners, while cooperation is not.

Question 9

What is the effect of high tryptophan levels on the trp operon?

Accepted Answer

The corepressor-repressor complex binds to the operator, blocking transcription.

Question 10

Which of the following best describes the effect of chlortetracycline treatment on aphids, as shown in the table?

Accepted Answer

Chlortetracycline reduces aphid weight, growth rate, and viable offspring, indicating disruption of Buchnera.

Question 11

Which of the following is a real-world example of commensalism?

Accepted Answer

Staphylococcus epidermidis consuming human waste products on skin without affecting human health.

Question 12

Which of the following best describes predation in microbial interactions?

Accepted Answer

One organism preys on another, such as Bdellovibrio entering the periplasmic space of Gram-negative bacteria.

Question 13

What is the main adverse effect that Streptomyces spp. have on other organisms?

Accepted Answer

Production of antibiotics that inhibit or kill other microbes (amensalism).

Question 14

Which of the following best describes competition in microbial interactions?

Accepted Answer

Two organisms try to acquire the same resource, and one may outcompete the other.

Question 15

Based on the graph showing Buchnera number, aphid weight, and bacteriocyte number, what happens during the reproductive period of the aphid?

Accepted Answer

Buchnera number and aphid weight peak, while bacteriocyte number declines.

Question 16

Which of the following is a plausible explanation for why aphids treated with chlortetracycline produce no viable offspring?

Accepted Answer

Chlortetracycline eliminates Buchnera, which is required for aphid reproduction.

Microbial Interactions: Symbiosis, Regulation, and the Human Microbiota

Study Guide - Practice Questions