Question 1

Which of the following best describes the difference between mutualism and cooperation in microbial interactions?

Accepted Answer

Mutualism is an obligatory relationship where both partners are dependent on each other, while cooperation is not obligatory and both partners can survive independently.

Question 2

In the aphid-Buchnera aphidicola mutualism, what is the primary benefit provided by Buchnera to the aphid?

Accepted Answer

Synthesis of essential amino acids that the aphid cannot obtain from its diet.

Question 3

Which of the following equations correctly represents the Calvin-Benson cycle used by chemolithotrophic bacteria in Riftia tube worms for carbon fixation?

Accepted Answer

$$6\ \mathrm{CO}_2 + 12\ \mathrm{NADPH} + 18\ \mathrm{ATP} \rightarrow C_6H_{12}O_6$ + 12\ \mathrm{NADP}^+ + 18\ \mathrm{ADP} + 18\ \mathrm{P_i}$$

Question 4

Which of the following is an example of amensalism in microbial interactions?

Accepted Answer

Production of antibiotics by Pseudonocardia bacteria that inhibit the growth of Escovopsis fungi in ant fungal gardens.

Question 5

Which of the following best describes the outcome of competition between two microbial species for a single limiting resource?

Accepted Answer

Either one species outcompetes the other (competitive exclusion), or both coexist at lower population levels.

Question 6

In the protozoan-termite symbiosis, what is the role of the bacterial endosymbionts within the protozoa?

Accepted Answer

They produce cellulase enzymes that allow the protozoa to digest cellulose from wood.

Question 7

Which of the following scenarios is an example of commensalism?

Accepted Answer

Initial colonizing bacteria in a biofilm modify the surface, allowing other microorganisms to attach.

Question 8

Which of the following statements about coral bleaching is correct?

Accepted Answer

It is caused by the loss or expulsion of zooxanthellae from coral tissues, often due to increased temperature.

Question 9

Which of the following is a distinguishing feature of parasitism compared to predation?

Accepted Answer

Parasitism typically does not result in the immediate death of the host, while predation usually does.

Question 10

Which of the following best describes the relationship between the mycobiont and phycobiont in lichens?

Accepted Answer

Controlled parasitism, where the fungal partner (mycobiont) provides shelter and minerals, but the algal or cyanobacterial partner (phycobiont) may grow faster without the fungus.

Question 11

Which of the following is an example of an epibiotic predator among microbes?

Accepted Answer

Vampirococcus, which attaches to the outer membrane of its prey and secretes degradative enzymes.

Question 12

Which of the following is a real-world example of amensalism involving multiple organisms?

Accepted Answer

Attine ants, Pseudonocardia bacteria, Leucocoprinus fungi, and Escovopsis fungi, where Pseudonocardia produces compounds that inhibit Escovopsis.

Question 13

Which of the following best describes the process of microbial succession during milk spoilage?

Accepted Answer

Fermenting bacteria produce acid waste, promoting the growth of more acid-tolerant species (commensalism).

Question 14

Which of the following is NOT a characteristic of mutualism?

Accepted Answer

One partner is harmed while the other benefits.

Question 15

Which of the following is a correct statement about the genomic features of Buchnera aphidicola?

Accepted Answer

It has an extremely reduced genome with about 75% of the ancestral genome eliminated.

Question 16

Which of the following is a possible outcome when two microbial species compete for the same resource?

Accepted Answer

Both species survive at lower population levels due to resource sharing.

Question 17

Which of the following best describes the role of chemolithotrophic bacteria in the Riftia tube worm mutualism?

Accepted Answer

They use hydrogen sulfide as an electron donor to fix inorganic carbon into organic compounds via the Calvin-Benson cycle.

Microbial Interactions: Types, Mechanisms, and Examples

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