Question 1

The gut flora is relatively stable over long time periods in healthy adults, suggesting its "fine- tuned" role.

Accepted Answer

Studies have shown that although the composition of the gut flora can vary from person to person, it is relatively stable over time in healthy individuals, indicating that it plays an important and finely-tuned role in the body.

Question 2

Bacterial cells themselves serve as major sources of protein and vitamins in hindgut fermenting animals.

Accepted Answer

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Question 3

The bacterium Escherichia coli comprises a significant fraction of the bacterial population in healthy adult humans, ranging from 10-50%.

Accepted Answer

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Question 4

The reproductive systems of many insects can be manipulated by parasitic symbionts, which are passed down to each generation and can skew the sex ratio of their progeny.

Accepted Answer

This statement is true. Many insects have symbiotic bacteria that can manipulate the sex ratio of their offspring, such as Wolbachia. These bacteria can either kill male offspring or bias the sex ratio towards females, depending on their reproductive interests.

Question 5

Provide a biochemical explanation of why a cow might eructate (belch).

Accepted Answer

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Question 6

Hydrogenosomes present in some anaerobic protists have yet to be identified in any other taxonomic group.

Accepted Answer

Hydrogenosomes have only been identified in certain anaerobic protists and have not been found in any other taxonomic group so far.

Question 7

Describe a way in which Hawaiian bobtail squids exclude all bacteria except Allivibrio fischeri into their light organ. Also explain how A. fischeri is capable of colonizing the organ.

Accepted Answer

The answer of Describe a way in which Hawaiian bobtail...

Question 8

Due to the close interactions with other organisms, microbial symbionts generally have larger genome sizes compared to other non- symbiotic bacteria.

Accepted Answer

Microbial symbionts often have reduced genome sizes due to the loss of genes that are redundant or unnecessary for their specialized lifestyle, relying on their host for certain functions.

Question 9

Provide an example of how an abrupt diet change in a rumen such as a cow can cause serious illnesses, even death. Also explain the processes that develop into sickness.

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Question 10

According to the free energy obtained from each product using CO2 and H2, methanogenesis is favored over acetogenesis. Why is this NOT the case in termites?

Accepted Answer

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Question 11

The mycelia of mycorrhizae can form underground nutrient networks where several trees are connected.

Accepted Answer

Mycorrhizal networks allow for the sharing of nutrients and other resources between multiple trees in a forest ecosystem.

Question 12

Molecular evidence suggests that leeches contain four distinct bacterial communities in its digestive tract.

Accepted Answer

The answer of Molecular evidence suggests that leeches contain four...

Question 13

Explain the role of the Ti plasmid in causing crown gall disease in plants.

Accepted Answer

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Question 14

Explain how leeches are used today in medical replants and transplants.

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Question 15

Two- thirds of terrestrial environments support growth of termites.

Accepted Answer

According to research, about two-thirds of terrestrial environments are suitable for termite growth.

Question 16

How do arbuscular mycorrhizae colonize roots?

Accepted Answer

The answer of How do arbuscular mycorrhizae colonize roots?...

Question 17

Several rhizobial species within a cross- inoculation group should be able to grow with particular legume species such as alfalfa, however the same cross- inoculation group would be unable to associate with other legumes species.

Accepted Answer

This statement is true. Rhizobial species within a cross- inoculation group have the ability to form effective nodules on some legume species but not on others. This is due to the specificity of the symbiotic relationship between the rhizobia and legumes. The degree of specificity varies among different cross-inoculation groups.

Question 18

Bacteroids are rarely found within plant cells.

Accepted Answer

Bacteroids are actually commonly found within plant cells that contain nitrogen-fixing rhizobia.

Question 19

Biogeography studies have identified 16S rRNA genes of green bacterial consortia from nearby lakes containing identical sequences.

Accepted Answer

Biogeography studies have indeed identified 16S rRNA genes of green bacterial consortia from nearby lakes containing identical sequences. This suggests that these similar bacteria are able to thrive in similar environmental conditions.

Question 20

Bacteria associated with plants fix approximately 25% of all nitrogen fixed annually on Earth.

Accepted Answer

Bacteria associated with plants, particularly those in the roots, form symbiotic relationships with the plants and are capable of fixing atmospheric nitrogen into a usable form for the plant. This process, known as biological nitrogen fixation, accounts for approximately 25% of all nitrogen fixed annually on Earth.

Quiz 25: Microbial Symbioses