Question 1

Gut symbionts are lost after each molting a termite undergoes.

Accepted Answer

A) True 
 B)False  True

Question 2

Molecular evidence suggests that leeches contain two distinct bacterial communities in their bladder.

Accepted Answer

A) True 
 B)False  True

Question 3

What is the difference between a primary and secondary insect symbiont? Propose how you might use an insect symbiont to control the spread of an insect-borne disease.

Accepted Answer

Primary symbionts are microorganisms that are required for the host insect to replicate.Secondary symbionts are not required for the insect to replicate,so they are not found in every member of the insect population.There are many different ways that an insect symbiont could be manipulated to control the spread of an insect-borne disease.One way is to use a secondary symbiont that manipulates the reproduction of the insect host,such as Buchnera species that sterilize uninfected females after mating with an infected male.Another possibility would be to use an antimicrobial to inhibit the primary symbiont of an insect such that the death of the primary symbiont would stop the insects from reproducing.

Question 4

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

Accepted Answer

A) True 
 B)False

Question 5

How are symbiotic relationships important in agriculture and food production? Use at least two different examples to support your answer and explain how understanding these symbioses could help produce more food.

Accepted Answer

Answers can use any two of the following

Question 6

Which of the following do dinoflagellates most commonly associate with in a mutualistic relationship?

Accepted Answer

A)  clams 
B)  corals 
C)  flatworms 
D)  snails 
A)  clams 
B)  corals 
C)  flatworms 
D)  snails

Question 7

The gut flora is relatively stable over long time periods in healthy adults,suggesting its highly evolved role in the human body.

Accepted Answer

A) True 
 B)False

Question 8

The structural and trophic foundation of coral reefs is a mutualistic relationship between

Accepted Answer

A)  cyanobacteria and sponges (Porifera). 
B)  chemolithotrophic bacteria and stony corals (Cnidaria). 
C)  dinoflagellates and stony corals (Cnidaria). 
D)  cyanobacteria and stony corals (Cnidaria). 
A)  cyanobacteria and sponges (Porifera). 
B)  chemolithotrophic bacteria and stony corals (Cnidaria). 
C)  dinoflagellates and stony corals (Cnidaria). 
D)  cyanobacteria and stony corals (Cnidaria).

Question 9

Ruminants digest bacterial cells as a primary source of

Accepted Answer

A)  carbohydrates. 
B)  vitamins and proteins. 
C)  proteins. 
D)  vitamins. 
A)  carbohydrates. 
B)  vitamins and proteins. 
C)  proteins. 
D)  vitamins.

Question 10

While rhizobia usually associate with plant roots,nodules can also be formed along the stems of leguminous plants.

Accepted Answer

A) True 
 B)False

Question 11

The mutualism of Azolla-Anabaena is useful for

Accepted Answer

A)  aquaculturalists. 
B)  corn farmers. 
C)  rice farmers. 
D)  tropical forest community succession. 
A)  aquaculturalists. 
B)  corn farmers. 
C)  rice farmers. 
D)  tropical forest community succession.

Question 12

Obligately symbiotic relationships generally do not foster horizontal gene transfer at a higher rate than non-symbiotic relationships.

Accepted Answer

A) True 
 B)False

Question 13

Weight gain and obesity may be partly caused by certain gut microbial communities that

Accepted Answer

A)  absorb more vitamins and essential amino acids. 
B)  produce more volatile fatty acids by fermentation. 
C)  stimulate the gut endothelium to absorb more sugars. 
D)  produce more hydrogen gas by fermentation. 
A)  absorb more vitamins and essential amino acids. 
B)  produce more volatile fatty acids by fermentation. 
C)  stimulate the gut endothelium to absorb more sugars. 
D)  produce more hydrogen gas by fermentation.

Question 14

The following quote is taken from a university extension publication for farmers:
"Grain poisoning,also known as grain overload or lactic acidosis,is usually the result of stock consuming large quantities of grain or pellets to which they are unaccustomed.Pasture-fed cows or feedlot cattle not yet adapted to grain may become acutely ill or die after eating only moderate amounts of grain,whereas stock accustomed to diets high in grain content may consume large amounts of grain with little or no effect."
What is happening in the digestive system of the livestock that causes grain poisoning and why does a gradual shift in diet avoid this problem?

Accepted Answer

A major shift in diet,where the rumen fl

Question 15

Which of the following is NOT a major question in the Human Microbiome Project?

Accepted Answer

A)  Are differences in the relative abundance of different bacteria important? 
B)  Do differences in the human microbiome correlate with differences in human health? 
C)  Is there a correlation between microbial population structure and host genotype? 
D)  How can we reduce the number of microbes on the human body? 
A)  Are differences in the relative abundance of different bacteria important? 
B)  Do differences in the human microbiome correlate with differences in human health? 
C)  Is there a correlation between microbial population structure and host genotype? 
D)  How can we reduce the number of microbes on the human body?

Question 16

Certain species of Bacteria have been identified to cause obesity.

Accepted Answer

A) True 
 B)False

Question 17

Horizontal gene transfer between host organisms and their symbionts

Accepted Answer

A)  happens frequently because of coevolution. 
B)  causes genome reduction in the symbiont and genome expansion in the host. 
C)  causes genome reduction in both the host and the symbiont. 
D)  has been observed, but is considered a rare event. 
A)  happens frequently because of coevolution. 
B)  causes genome reduction in the symbiont and genome expansion in the host. 
C)  causes genome reduction in both the host and the symbiont. 
D)  has been observed, but is considered a rare event.

Question 18

Why do obligate symbionts often contain lower G+C content when compared to free-living organisms?

Accepted Answer

A)  Ancestral symbionts had low GC content genomes by chance, and these low GC content genomes are passed onto their progeny. 
B)  Free-living organisms must have a more stable genome to survive; low G+C content organisms are often selected against in nature. 
C)  Replicating high G+C content genomes requires several additional enzymes, to break apart the strong triple bonds formed from GC pairs, which are rarely found in symbionts with relatively small genome sizes. 
D)  Symbionts usually do not have as many DNA repair mechanisms as free-living organisms, and two common spontaneous mutations change GC pairs into AT pairs. 
A)  Ancestral symbionts had low GC content genomes by chance, and these low GC content genomes are passed onto their progeny. 
B)  Free-living organisms must have a more stable genome to survive; low G+C content organisms are often selected against in nature. 
C)  Replicating high G+C content genomes requires several additional enzymes, to break apart the strong triple bonds formed from GC pairs, which are rarely found in symbionts with relatively small genome sizes. 
D)  Symbionts usually do not have as many DNA repair mechanisms as free-living organisms, and two common spontaneous mutations change GC pairs into AT pairs.

Question 19

Coral bleaching is primarily caused by antimicrobials that disrupt the mutualistic relationships formed between corals and their bacterial symbionts.

Accepted Answer

A) True 
 B)False

Question 20

The specificity of certain rhizobia to infect only particular plants is in part due to the

Accepted Answer

A)  abundance of nutrients present in the soil. 
B)  nifH genes they possess. 
C)  rhizobial lipids that act as signaling molecules. 
D)  season (time of year). 
A)  abundance of nutrients present in the soil. 
B)  nifH genes they possess. 
C)  rhizobial lipids that act as signaling molecules. 
D)  season (time of year).

Exam 22: Microbial Symbioses

Gut symbionts are lost after each molting a termite undergoes.

Molecular evidence suggests that leeches contain two distinct bacterial communities in their bladder.

What is the difference between a primary and secondary insect symbiont? Propose how you might use an insect symbiont to control the spread of an insect-borne disease.

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

How are symbiotic relationships important in agriculture and food production? Use at least two different examples to support your answer and explain how understanding these symbioses could help produce more food.

Which of the following do dinoflagellates most commonly associate with in a mutualistic relationship?

The gut flora is relatively stable over long time periods in healthy adults,suggesting its highly evolved role in the human body.

The structural and trophic foundation of coral reefs is a mutualistic relationship between

Ruminants digest bacterial cells as a primary source of

While rhizobia usually associate with plant roots,nodules can also be formed along the stems of leguminous plants.

The mutualism of Azolla-Anabaena is useful for

Obligately symbiotic relationships generally do not foster horizontal gene transfer at a higher rate than non-symbiotic relationships.

Weight gain and obesity may be partly caused by certain gut microbial communities that

Which of the following is NOT a major question in the Human Microbiome Project?

Certain species of Bacteria have been identified to cause obesity.

Horizontal gene transfer between host organisms and their symbionts

Why do obligate symbionts often contain lower G+C content when compared to free-living organisms?

Coral bleaching is primarily caused by antimicrobials that disrupt the mutualistic relationships formed between corals and their bacterial symbionts.

The specificity of certain rhizobia to infect only particular plants is in part due to the

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