Question 1

In April 2010 an oil rig blowout resulted in a major crude oil spill in the Gulf of Mexico. How was the majority of the crude oil cleaned out of the Gulf?
A) Humans collected the oil from the surface of the water and along the coastline.
B) Artificial bioremediation, crude-oil eating microbes were poured into the ocean.
C) Natural bioremediation by microbes already present in the ocean.
D) Both human collection of oil and artificial bioremediation.
E) The crude oil still has not been cleaned up.

Accepted Answer

Natural bioremediation by microbes already present in the ocean played a significant role in cleaning up the majority of the crude oil from the 2010 Gulf of Mexico spill. These microbes are capable of breaking down oil into less harmful substances.

Question 2

Which of the following is the best definition of antagonism?
A) competition for limited resources
B) cooperation in utilization of resources
C) microbes living in the same environment without harming each other
D) microbes producing products that interfere with the growth of others
E) competition and producing products that interfere with growth

Accepted Answer

Antagonism refers to the interaction between microorganisms in which one produces substances that inhibit or prevent the growth of another microorganism. This definition is best reflected in choice D, which states that antagonism involves microbes producing products that interfere with the growth of others.

Question 3

What is carbon fixation?
A) The conversion of dead organisms into fossil fuel.
B) The release of carbon dioxide by cellular respiration.
C) The conversion of carbon dioxide into organic molecules.
D) The storage of carbon compounds by heterotrophs.
E) The release of carbon dioxide by combustion.

Accepted Answer

Carbon fixation is the process by which carbon dioxide from the atmosphere is converted into organic molecules such as glucose by autotrophic organisms like plants. This process usually involves photosynthesis, which utilizes the energy of sunlight to power the conversion of carbon dioxide into usable organic compounds.

Question 4

The use of microorganisms to clean a polluted environment is
A) bioremediation.
B) antagonism.
C) cooperation.
D) genetic engineering.
E) waste treatment.

Accepted Answer

Bioremediation is the use of microorganisms to break down or remove pollutants from an environment. This process is often more sustainable and cost-effective than traditional methods of pollution clean-up.

Question 5

What type of reactions take place in the portion of the sulfur cycle indicated in the figure?
A) oxidation-reduction
B) fermentation
C) dissimilation
D) denitrification
E) carbon fixation

Accepted Answer

The portion of the sulfur cycle indicated in the figure involves the conversion of sulfate (SO42-) to hydrogen sulfide (H2S) by sulfate-reducing bacteria. This is an example of an oxidation-reduction reaction, as electrons are transferred from sulfate to hydrogen to produce H2S.

Question 6

A microbiome is composed of
A) biospheres.
B) microhabitats.
C) ecosystems.
D) populations
E) sets of guilds.

Accepted Answer

A microbiome is composed of sets of guilds, which are groups of microorganisms that exploit the same resources in a similar way.

Question 7

What is nitrogen fixation?
A) the conversion of nitrate (NO₃⁻) into nucleic acids
B) the incorporation of ammonia (NH₃) into amino acids
C) the release of ammonia (NH₄⁻) from decomposing organic material
D) the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃)
E) the conversion of ammonia (NH₃) into ammonium ion (NH₄⁺)

Accepted Answer

Nitrogen fixation is the process of converting atmospheric nitrogen gas (N₂) into a form that can be used by living organisms, usually ammonia (NH₃). This process is carried out by certain bacteria and can occur naturally through lightning or human activities such as the Haber process.

Question 8

What type(s) of microbial interactions take place in a microhabitat?
A) antagonism
B) cooperation
C) competition
D) antagonism and competition
E) a combination of antagonism, cooperation and competition

Accepted Answer

Microbial interactions in a microhabitat can involve antagonism, cooperation, and competition. For example, one species may produce a compound that inhibits the growth of another species (antagonism). Alternatively, two species may work together to break down a complex substrate, such as cellulose, into simpler molecules (cooperation). Finally, multiple species may compete for the same resources, such as a limited supply of nutrients. Therefore, a combination of antagonism, cooperation, and competition occurs in a microhabitat.

Question 9

The greatest diversity of the human microbiome is found
A) on the skin.
B) in the mouth.
C) in the intestine.
D) in the urinary system.
E) in the respiratory system.

Accepted Answer

The greatest diversity of the human microbiome is found in the intestine. The large intestine alone is estimated to contain up to 100 trillion microorganisms, including bacteria, viruses, fungi, and other microbes. This diverse community of microorganisms is important for digestion, immune function, and other physiological processes. While the skin and mouth also harbor significant amounts of microbial diversity, the intestine is the site of greatest diversity. The urinary and respiratory systems have relatively low levels of microbial diversity.

Question 10

Which of the following is the conversion of ammonium ion⁺ into nitrogen gas (N₂)?
A) assimilation
B) anammox
C) nitrogen fixation
D) nitrification
E) denitrification

Accepted Answer

Anammox (anaerobic ammonium oxidation) is the process where ammonium ions are converted into nitrogen gas under anaerobic conditions.

Question 11

A guild is composed of
A) populations with similar metabolic activities.
B) microhabitats in a single location.
C) a single species.
D) microbiomes in a single zone.
E) ecosystems.

Accepted Answer

A guild consists of groups of species that exploit the same kinds of resources in similar ways, which is closely related to having similar metabolic activities.

Question 12

Which of the following is the CORRECT sequence of microbial associations from smallest to largest?
A) populations, guilds, communities, microhabitats, ecosystem
B) populations, communities, microhabitats, ecosystem, guilds
C) communities, microhabitats, ecosystem, guilds, populations
D) populations, communities, ecosystem, guilds, microhabitats
E) ecosystem, populations, communities, microhabitats, guilds

Accepted Answer

The correct sequence from smallest to largest in terms of microbial associations is: populations (groups of individuals of the same species), guilds (groups of species exploiting the same resources in a similar way), communities (all the populations in a specific area), microhabitats (specific environments within a habitat where microbial communities can vary), and ecosystem (a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system).

Question 13

Which of the following oxidize H₂S to SO₄⁻², the form of sulfur animals use for their metabolism?
A) Beggiatoa
B) Desulfovibrio
C) purple sulfur bacteria
D) both Beggiatoa and purple sulfur bacteria
E) both Beggiatoa and Desulfovibrio

Accepted Answer

Beggiatoa and purple sulfur bacteria are known to oxidize H₂S to SO₄²⁻, which is the form of sulfur used in animal metabolism. Desulfovibrio, on the other hand, is known for reducing sulfates to sulfides, not oxidizing H₂S.

Question 14

Which of the following statements concerning the phosphorus cycle in bacteria is TRUE?
A) The element cycles between different organic molecules.
B) It is the most important process for synthesizing proteins and nucleic acids.
C) The element alternates among several oxidative states.
D) The element changes from insoluble to soluble forms.
E) The element is converted to a gaseous state and is lost to the environment.

Accepted Answer

In the phosphorus cycle, bacteria play a crucial role in converting insoluble forms of phosphorus (such as phosphate minerals) into soluble forms that plant roots can absorb. This conversion from insoluble to soluble forms is a key feature of the phosphorus cycle.

Question 15

What nutrient most commonly contributes to eutrophication?
A) phosphorus
B) nitrite
C) sulfide
D) methane
E) iron oxides

Accepted Answer

Phosphorus is the most commonly identified nutrient that contributes to eutrophication. Phosphorus is often found in fertilizers, detergents, and sewage and can stimulate excessive growth of algae and other aquatic plants, leading to oxygen depletion and harm to aquatic animal life.

Question 16

What is the source of the acidic pH of some mine runoff?
A) Iron ores are reduced by exposure to the atmosphere.
B) Pyrite is oxidized by exposure to the atmosphere and microbes.
C) Iron ores contain sulfuric acid (H₂SO₄).
D) Sulfur-containing ores are reduced by exposure to oxygen.
E) Hydrogen gas trapped in ore reacts with the atmosphere to produce hydrochloric acid (HCl).

Accepted Answer

Pyrite, also known as fool's gold, is a common mineral in many ores found in mines. When pyrite is exposed to oxygen and microbes, it oxidizes and produces sulfuric acid (H₂SO₄), which lowers the pH of the mine runoff. This process is known as acid mine drainage (AMD).

Question 17

Which form of sulfur can algae and plants use but not produce?
A) hydrogen sulfide (H₂S)
B) elemental sulfur (S⁰)
C) sulfuric acid (H₂SO₄)
D) sulfate (SO₄²⁻ )
E) both elemental sulfur and hydrogen sulfide

Accepted Answer

Algae and plants can only use sulfate (SO4²⁻) as a form of sulfur for making amino acids, proteins, and other biomolecules. They are not capable of producing sulfate, but they are able to take up sulfate ions from the environment and use them for growth and metabolism. Hydrogen sulfide and elemental sulfur are reduced forms of sulfur that can be used by certain bacteria, but not algae and plants. Sulfuric acid is a highly reactive and corrosive compound that is not commonly found in the environment as a source of sulfur for organisms.

Question 18

A ________ is a single species in an environment.
A) microhabitat
B) population
C) colony
D) biome
E) guild

Accepted Answer

A population refers to a group of individuals of the same species living in the same area and interacting with each other. A microhabitat is a small-scale habitat within a larger habitat. A colony refers to a group of individuals of the same species living together, but it can also include different types of individuals, such as worker ants and a queen ant. A biome is a large-scale terrestrial ecosystem characterized by specific climate and vegetation types. A guild is a group of species that exploit the same type of resources in similar ways. Therefore, the best choice for a single species in an environment is a population.

Question 19

The "greenhouse gas" methane is produced by
A) prokaryotes.
B) fungi.
C) algae.
D) animals.
E) both fungi and alga.

Accepted Answer

Methane is primarily produced by prokaryotes known as methanogens, which are a type of archaea.

Question 20

Which of the following best describes the roles of microorganisms in the carbon cycle?
A) primary producers
B) heterotrophs
C) decomposers
D) heterotrophs and decomposers
E) primary producers, heterotrophs and decomposers

Accepted Answer

Microorganisms play a variety of roles in the carbon cycle. They act as primary producers (e.g., cyanobacteria and algae) by fixing carbon dioxide during photosynthesis. They also function as heterotrophs, consuming organic matter for energy, and as decomposers, breaking down dead organic material and releasing carbon dioxide back into the atmosphere. Therefore, they fulfill all three roles: primary producers, heterotrophs, and decomposers.

Quiz 26: Microbial Ecology and Microbiomes

In April 2010 an oil rig blowout resulted in a major crude oil spill in the Gulf of Mexico. How was the majority of the crude oil cleaned out of the Gulf?

Which of the following is the best definition of antagonism?

What is carbon fixation?

The use of microorganisms to clean a polluted environment is

What type of reactions take place in the portion of the sulfur cycle indicated in the figure?

A microbiome is composed of

What is nitrogen fixation?

What type(s) of microbial interactions take place in a microhabitat?

The greatest diversity of the human microbiome is found

Which of the following is the conversion of ammonium ion⁺ into nitrogen gas (N₂) ?

A guild is composed of

Which of the following is the CORRECT sequence of microbial associations from smallest to largest?

Which of the following oxidize H₂S to SO₄⁻², the form of sulfur animals use for their metabolism?

Which of the following statements concerning the phosphorus cycle in bacteria is TRUE?

What nutrient most commonly contributes to eutrophication?

What is the source of the acidic pH of some mine runoff?

Which form of sulfur can algae and plants use but not produce?

A ________ is a single species in an environment.

The "greenhouse gas" methane is produced by

Which of the following best describes the roles of microorganisms in the carbon cycle?