Question 1

This bacterium derives nutrition by digesting human intestinal contents (in other words,food).Thus,this bacterium should be an

Accepted Answer

The bacterium is digesting human intestinal contents, indicating that it is deriving nutrition from organic compounds (heterotroph). It is also living in the human intestine, which is anaerobic (lack of oxygen), indicating that it is an anaerobic chemoheterotroph.

Question 2

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell.Hfr cell DNA begins entering the recipient cell at Time A.Assume that reciprocal crossing over occurs (in other words,a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).Use this figure to answer the following questions.
 
-How is the recipient cell different at Time D than it was at Time A?

Accepted Answer

The answer of The figure below depicts changes to the...

Question 3

Use the following information to answer the questions below.
Nitrogenase,the enzyme that catalyzes nitrogen fixation,is inhibited whenever free O₂ reaches a critical concentration.Consequently,nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂.Consider the colonial aquatic cyanobacterium,Anabaena,whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighbouring cells.Intracellular connections allow heterocysts to transport fixed nitrogen to neighbouring cells in exchange for carbohydrates."
-Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen,what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
1)couple them with photosystem II (the photosystem that splits water molecules)
2)package them in membranes that are impermeable to all gases
3)be obligate anaerobes
4)be strict aerobes
5)package these enzymes in specialized cells or compartments that inhibit oxygen entry

Accepted Answer

Nitrogen-fixing prokaryotes might be obligate anaerobes, avoiding oxygen to protect nitrogenase, or package these enzymes in specialized cells or compartments that inhibit oxygen entry, like the heterocysts of Anabaena.

Question 4

In which feature(s)should one be able to locate a complete chromosome of this bacterium?
1)nucleolus
2)prophage
3)endospore
4)nucleoid

Accepted Answer

The paragraph states that the bacterium "contains no plasmids and relatively little peptidoglycan," but it does not mention any other structures besides the features listed in the answer choices. The only option that refers to a structure in bacteria where the chromosome is located is nucleoid (4).

Question 5

For several decades now,amphibian species worldwide have been in decline.A significant proportion of the decline seems to be due to the spread of the chytrid fungus,Batrachochytrium dendrobatidis (Bd).Chytrid sporangia reside within the epidermal cells of infected animals,animals that consequently show areas of sloughed skin.They can also be lethargic,which is expressed through failure to hide and failure to flee.The infection cycle typically takes four to five days,at the end of which zoospores are released from sporangia into the environment.In some amphibian species,mortality rates approach 100%; other species seem able to survive the infection.
-If infection primarily involves the outermost layers of adult amphibian skin,and if the chytrids use the skin as their sole source of nutrition,then which term best applies to the chytrids?

Accepted Answer

Based on the information given, the chytrids appear to be using the amphibian skin as their source of nutrition, which implies that they are consuming organic molecules from the skin. Therefore, they would be classified as chemoheterotrophs. Additionally, the presence of zoospores suggests that they are capable of moving and therefore would require oxygen, indicating they are aerobic. Therefore, the best choice is D, which describes an aerobic chemoheterotroph.

Question 6

The following table depicts characteristics of five prokaryotic species (A-E).Use the information in the table to answer the following questions.
 
-Which species should be able to respond most readily to taxes (plural of taxis)?

Accepted Answer

Species C should be able to respond most readily to taxes because taxis is a directed movement toward or away from a stimulus, and species with the ability to move or change direction in response to environmental cues would be most adept at this behavior.

Question 7

What should be true of the cell wall of this bacterium?

Accepted Answer

The presence of an outer membrane composed of lipopolysaccharide is a characteristic of Gram-negative bacteria, and distinguishes them from Gram-positive bacteria.

Question 8

Which question,arising from the results depicted in the above figure,is most interesting from a genetic perspective,and has the greatest potential to increase our knowledge base?

Accepted Answer

The answer of Which question,arising from the results depicted in...

Question 9

Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense)to proteins that

Accepted Answer

The answer of Some of the proteins that allow this...

Question 10

Use the information in the following paragraph to answer the next few questions.
A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining.It adheres to the intestinal lining using a feature that also protects it from phagocytes,bacteriophages,and dehydration.Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium,even after being mixed with water and boiled.The bacterium is not susceptible to the penicillin family of antibiotics.It contains no plasmids and relatively little peptidoglycan.
-Adherence to the intestinal lining by this bacterium is due to its possession of

Accepted Answer

The bacterium's ability to adhere to the intestinal lining and its protection from phagocytes, bacteriophages, and dehydration suggest it possesses a capsule. Capsules are known for these protective roles and for facilitating adherence to surfaces.

Question 11

Use the following information to answer the questions below.
Nitrogenase,the enzyme that catalyzes nitrogen fixation,is inhibited whenever free O₂ reaches a critical concentration.Consequently,nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂.Consider the colonial aquatic cyanobacterium,Anabaena,whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighbouring cells.Intracellular connections allow heterocysts to transport fixed nitrogen to neighbouring cells in exchange for carbohydrates."
-Which two questions below arise from a careful reading of this quotation,and are most important for understanding how N₂ enters heterocysts,and how O₂ is kept out of heterocysts?
1)If carbohydrates can enter the heterocysts from neighbouring cells via the "intracellular connections," how is it that O₂ doesn't also enter via this route?
2)If the cell walls of Anabaena's photosynthetic cells are permeable to O₂ and CO₂,are they also permeable to N₂?
3)If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation,how can these cells fail to perform nitrogen fixation?
4)If the nuclei of the heterocysts contain the genes that code for photosynthesis,how can these cells fail to perform photosynthesis?
5)If the cell walls of Anabaena's heterocysts are permeable to N₂,how is it that N₂ doesn't diffuse out of the heterocysts before it can be fixed?
6)If the thick cell walls of the heterocysts exclude entry of oxygen gas,how is it that they don't also exclude the entry of nitrogen gas?

Accepted Answer

Questions 1 and 6 are most important for understanding how N₂ enters heterocysts and how O₂ is kept out. They address the potential problem of O₂ diffusing into heterocysts through intracellular connections and the potential problem of N₂ diffuse out of the heterocysts before it can be fixed due to the permeability of the cell walls. The other questions are not as relevant to this specific issue.

Question 12

Consider the thermoacidophile,Sulfolobus acidocaldarius.Which of the following graphs most accurately depicts the expected temperature and pH profiles of its enzymes? (Note: The horizontal axes of these graphs are double,with pH above and temperature below.)

Accepted Answer

The answer of Consider the thermoacidophile,Sulfolobus acidocaldarius.Which of the following...

Question 13

This bacterium derives nutrition by digesting human intestinal contents (in other words,food).Humans lacking this bacterium have no measurable reproductive advantage or disadvantage relative to humans who harbour this bacterium.Consequently,the bacterium can be properly described as which of the following?
1)symbiont
2)endosymbiont
3)mutualist
4)commensal

Accepted Answer

The answer of This bacterium derives nutrition by digesting human...

Question 14

The following table depicts characteristics of five prokaryotic species (A-E).Use the information in the table to answer the following questions.
 
-Which two species should have much more phospholipid,in the form of bilayers,in their cytoplasms than most other bacteria?

Accepted Answer

The answer of The following table depicts characteristics of five...

Question 15

Use the information in the following paragraph to answer the next few questions.
A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining.It adheres to the intestinal lining using a feature that also protects it from phagocytes,bacteriophages,and dehydration.Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium,even after being mixed with water and boiled.The bacterium is not susceptible to the penicillin family of antibiotics.It contains no plasmids and relatively little peptidoglycan.
-This bacterium's ability to survive in a human who is taking penicillin pills may be due to the presence of
1)penicillin-resistance genes.
2)a secretory system that removes penicillin from the cell.
3)a gram-positive cell wall.
4)a gram-negative cell wall.
5)an endospore.

Accepted Answer

The answer of Use the information in the following paragraph...

Question 16

During which two times can the recipient accurately be described as "recombinant: due to the sequence of events portrayed in the above figure?

Accepted Answer

The answer of During which two times can the recipient...

Question 17

Which two processes are responsible for the shape of the curve at Time B?
1)transduction
2)entry of single-stranded Hfr DNA
3)rolling circle replication of single-stranded Hfr DNA
4)activation of DNA pumps in plasma membrane

Accepted Answer

The shape of the curve at Time B is due to the processes of entry of single-stranded Hfr DNA and rolling circle replication of single-stranded Hfr DNA. Entry of single-stranded Hfr DNA leads to a gradual increase in the amount of DNA in the recipient cell, while rolling circle replication of single-stranded Hfr DNA leads to the production of long, linear DNA molecules that are seen as a plateau in the curve. Transduction and activation of DNA pumps in the plasma membrane are not responsible for the shape of the curve at Time B.

Question 18

The figure below depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell.Hfr cell DNA begins entering the recipient cell at Time A.Assume that reciprocal crossing over occurs (in other words,a fragment of the recipient's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA).Use this figure to answer the following questions.
 
-What is occurring at Time C that is decreasing the DNA content?

Accepted Answer

At Time C, the DNA content is decreasing because it is the degradation of DNA that was not retained in the recipient's chromosome. As the Hfr cell DNA enters the recipient cell, there is a possibility that not all the DNA will be exchanged through crossing over, and some fragments may remain unincorporated. These unincorporated fragments will eventually be degraded, resulting in a decrease in DNA content.

Question 19

For several decades now,amphibian species worldwide have been in decline.A significant proportion of the decline seems to be due to the spread of the chytrid fungus,Batrachochytrium dendrobatidis (Bd).Chytrid sporangia reside within the epidermal cells of infected animals,animals that consequently show areas of sloughed skin.They can also be lethargic,which is expressed through failure to hide and failure to flee.The infection cycle typically takes four to five days,at the end of which zoospores are released from sporangia into the environment.In some amphibian species,mortality rates approach 100%; other species seem able to survive the infection.
-Data were collected from the heterocysts of a nitrogen-fixing cyanobacterium inhabiting equatorial ponds.Study the following graph and choose the most likely explanation for the shape of the curve.

Accepted Answer

The answer of For several decades now,amphibian species worldwide have...

Question 20

The cell also lacks F factors and F plasmids.Upon its death,this bacterium should be able to participate in

Accepted Answer

The bacterium lacks F factors and F plasmids, which are required for conjugation. It also lacks bacteriophages, which are needed for transduction. Therefore, the only possibility for it to participate in horizontal gene transfer is through transformation, where it can take up DNA from the environment.

Quiz 27: Bacteria and Archaea

This bacterium derives nutrition by digesting human intestinal contents (in other words,food) .Thus,this bacterium should be an

In which feature(s) should one be able to locate a complete chromosome of this bacterium? 1) nucleolus 2) prophage 3) endospore 4) nucleoid

The following table depicts characteristics of five prokaryotic species (A-E) .Use the information in the table to answer the following questions. -Which species should be able to respond most readily to taxes (plural of taxis) ?

What should be true of the cell wall of this bacterium?

Which question,arising from the results depicted in the above figure,is most interesting from a genetic perspective,and has the greatest potential to increase our knowledge base?

Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense) to proteins that

Consider the thermoacidophile,Sulfolobus acidocaldarius.Which of the following graphs most accurately depicts the expected temperature and pH profiles of its enzymes? (Note: The horizontal axes of these graphs are double,with pH above and temperature below.)

The following table depicts characteristics of five prokaryotic species (A-E) .Use the information in the table to answer the following questions. -Which two species should have much more phospholipid,in the form of bilayers,in their cytoplasms than most other bacteria?

During which two times can the recipient accurately be described as "recombinant: due to the sequence of events portrayed in the above figure?

Which two processes are responsible for the shape of the curve at Time B? 1) transduction 2) entry of single-stranded Hfr DNA 3) rolling circle replication of single-stranded Hfr DNA 4) activation of DNA pumps in plasma membrane

The cell also lacks F factors and F plasmids.Upon its death,this bacterium should be able to participate in