Deck 22: Microbes in Global Elemental Cycles

Question 1

Concerning biogeochemical cycles, all of the following are true EXCEPT:

A) nearly half of nitrogen in the biosphere comes from anthropogenic sources
B) carbon dioxide production by human industry has outpaced fixation
C) most microbes can interconvert the six major elements, from one to another
D) organisms acquire elements from abiotic sources or from other organisms
E) biogeochemistry is the metabolic interactions of microbes with biotic and abiotic environs

Answer 1

C

Question 2

The element with the highest percentage of dry weight in bacteria is:

A) calcium
B) carbon
C) hydrogen
D) nitrogen
E) phosphorus

Answer 2

B

Question 3

Marine dead zones are characterized as being:

A) hypoxic
B) aerated
C) devoid of fish
D) dangerous for ship sail
E) both A and C

Answer 3

E

Question 4

The NASA FLUXNET tower is used for sampling and monitoring which of the following?

A) atmospheric CO₂ and carbon flux
B) dinitrogen gas and denitrification
C) biomass carbon and dissolved CO₂ oceans
D) hydrogen cycle and carbon flux
E) atmospheric nitrogen and carbon

Question 5

Oil spills introduce huge amounts of carbon in the environment. Which of the following techniques is used to quantify carbon influx and efflux of CO₂?

A) gas chromatography
B) mass spectroscopy
C) radioisotope incorporation
D) stable isotope ratios
E) none of the above

Question 6

Microbes participate in which step of wastewater treatment?

A) preliminary
B) primary
C) secondary
D) tertiary
E) all of the above

Question 7

Which of the following reservoirs contains the most rapidly cycled carbon?

A) the atmosphere
B) ocean biomass
C) ocean inorganic molecules
D) land biomass
E) crust below land and ocean

Question 8

Which of the following would decrease the amount of carbon dioxide in the atmosphere?

A) burning of logs
B) microbial decomposition of logs
C) increase in photosynthesis by plants
D) anaerobic decay of debris
E) increase in respiration by animals

Question 9

Which of the following is an anaerobic respiration reaction?

A) conversion of phosphine to phosphate
B) methanogenesis
C) photolysis of hydrogen sulfide to sulfur
D) precipitation of ferric iron with hydroxide
E) nitrogen fixation

Question 10

In the marine photic zone, the rate of photosynthesis:

A) is equal to the amount of CO₂ released from the niche
B) exceeds the rate of respiration
C) is less than the respiration rate
D) does not affect carbon cycling
E) is inversely related to rate of respiration

Question 11

The sink of an element in the ecosystem:

A) is the reservoir to which it returns during cycling
B) is the most accessible reservoir of that element
C) renders the element inaccessible
D) releases the element into the subsurface
E) is the source of the element for living organisms

Question 12

Much of the carbon and nitrogen in wetlands is cycled by:

A) aerobic respiration
B) plants and aerobic heterotrophs
C) wild fire
D) anaerobic bacteria and archaea such as methanogens
E) cyanobacteria and phototrophs

Question 13

The relative composition of elements across all species is:

A) constant
B) varied
C) not measurable
D) independent of abiotic factors
E) called its "reservoir"

Question 14

The largest reservoir for carbon is:

A) the atmosphere
B) ocean biomass
C) carbonate rocks and subsurface carbon
D) wetlands
E) fossil fuels

Question 15

Microbial activities in rice paddies increase the release of methane. What will happen if the rice paddy sediments are aerated?

A) More methane will be released.
B) More carbon dioxide will be released.
C) Methane release will be unaffected.
D) More nitrous oxide will be released.
E) More ammonia will be released.

Question 16

Which of the following is a macronutrient?

A) carbon
B) iron
C) zinc
D) phosphorus
E) nitrogen

Question 17

Ammonium nitrate addition to wetland soil cores is associated with increased CO₂ efflux, presumably caused by the increased respiration by:

A) phototrophs
B) autotrophs
C) heterotrophs
D) lithotrophs
E) methanogens

Question 18

Which of the following is correct about micronutrients?

A) They are needed in small amounts and do not need to be cycled.
B) They are sometimes needed in large amounts.
C) Phosphorus is a good example of a micronutrient.
D) Some microbes can grow without them.
E) Their cycling involves changes in oxidation state.

Question 19

Which of the following is NOT an example of a reduced form of carbon in the carbon cycle?

A) methane
B) biomass
C) hydrocarbons
D) carbon dioxide
E) methanol

Question 20

The release of CO₂ by human industry has/is __________ the rate of CO₂ fixation globally.

A) equal to
B) tripled
C) outpaced
D) far less than
E) none of the above

Question 21

Wastewater treatment generates which of the following gases in quantities sufficient for recovery as fuel?

A) carbon dioxide
B) oxygen
C) nitrous oxide
D) methane
E) hydrogen sulfide

Question 22

The highly potent greenhouse gas N₂O generates how many times the warming effect of CO₂?

A) 50
B) 100
C) 150
D) 200
E) 500

Question 23

Dinitrogen gas constitutes __________ of the atmosphere.

A) 10%
B) 79%
C) 69%
D) 21%
E) 0.03%

Question 24

In the anammox reaction, ___________ is the electron donor and _____________ is the electron acceptor.

A) dinitrogen gas; nitrite
B) nitrite; nitrate
C) ammonium ion; dinitrogen gas
D) dinitrogen gas; nitrate
E) ammonium ion; nitrite

Question 25

During wastewater treatment, the secondary treatment requires continual aeration to:

A) suppress microbial growth
B) select for anaerobic heterotrophs
C) stimulate abiotic degradation
D) increase microaerophilic filamentous bacteria
E) maximize breakdown of molecules to CO₂ and nitrates

Question 26

Microbes using nitrogen as a terminal electron acceptor would be performing:

A) nitrogen fixation
B) ammonification
C) nitrification
D) denitrification
E) anammox

Question 27

What do wastewater treatment plants have in common with wetland filtration (purification)?

A) the type of wastewater treated is the same
B) the engineering designs and flow are similar
C) they depend on microbes to remove nitrogen and carbon
D) chlorine is used to decontaminate pollutants
E) they are both continually aerated

Question 28

Which of the following major elements has the highest number of oxidation states?

A) nitrogen
B) carbon
C) hydrogen
D) sulfur
E) oxygen

Question 29

Which is the most stable form of nitrogen?

A) NO
B) NO^2-
C) N₂
D) NH₃
E) NH

Question 30

In polluted ocean waters, what type of organisms may contribute significantly to global warming?

A) photosynthetic algae
B) methanogens
C) vent bacteria
D) marine mammals
E) denitrifying bacteria

Question 31

Which of these is involved in commercial chemical fertilizer production?

A) lightning strikes
B) Haber process
C) cellular nitrogen fixation
D) nitrification
E) denitrification

Question 32

Biological nitrogen fixation (BNF) is inhibited by oxygen. Which of the following statements is NOT correct?

A) Nitrogen fixation is ubiquitous in soil and water.
B) Cyanobacteria are among the significant prokaryotic nitrogen fixers.
C) BNF was the major source of fixed N before the Industrial Revolution.
D) Only anaerobes fix dinitrogen on land.
E) A wide diversity of prokaryotes use the same enzyme-nitrogenase for nitrogen fixation.

Question 33

Which of the following would be more problematic in Kansas than Florida?

A) mercury-contaminated fish
B) nitrite-induced blue baby syndrome
C) uranium-contaminated soil
D) iron-corroded pipes
E) sulfur-contaminated coal

Question 34

Which of the following is responsible for purifying the majority of wastewater in the United States?

A) septic systems
B) wastewater treatment plants
C) landfills
D) wetlands
E) oceans

Question 35

Which contaminant in water is especially prevalent in agricultural regions of the United States?

A) carbon
B) sulfur
C) phosphate
D) nitrate
E) magnesium

Question 36

Which of the following organisms does NOT play a major role in secondary wastewater treatment?

A) Zoogloea
B) Flavobacterium
C) Escherichia
D) Pseudomonas
E) Nostoc

Question 37

What types of bacteria will carry out nitrification (conversion of ammonia to nitrite or nitrate)?

A) lithotrophs
B) heterotrophs
C) chemoorganotrophy
D) phototrophs
E) fastidious heterotrophs

Question 38

Deamination of amino acids (removal of the N) is an example of:

A) nitrogen fixation
B) nitrification
C) nitrate assimilation
D) ammonification
E) denitrification

Question 39

Why do farmers apply isoflavonoids to their fields?

A) to decrease the amount of oxygen
B) to increase the amount of carbon
C) to decrease the number of plant pathogens
D) to increase the number of nitrogen-fixing bacteria
E) to directly stimulate plant growth

Question 40

Which of the following is most responsible for perturbing the nitrogen cycle?

A) burning of fossil fuels
B) microbial nitrogen fixation
C) application of commercial fertilizer
D) assimilatory denitrification by plants
E) wastewater plant discharge into the environment

Question 41

What would happen if household wastewater was emptied into local receiving rivers without prior treatment?

Question 42

Predict the relative levels of biological oxygen demand (BOD) of water flowing into and out of a municipal wastewater treatment plant. Why is this difference desirable?

Question 43

Describe the wetland system set up by a hog farmer to treat his hog-farm waste.

Question 44

In 2010, the Deepwater Horizon oil well explosion resulted in the death of a great deal of wildlife and caused substantial environmental damage. Explain how bacteria played both harmful and useful roles (from our perspective) following this event.

Question 45

Which of the following is least likely to raise the biochemical oxygen demand?

A) nitrate
B) phosphate
C) sulfate
D) iron
E) organic fertilizer

Question 46

Which of the following spontaneously ignites with a green glow as it emanates from the ground?

A) pyrite
B) nitrous oxide
C) dimethyl sulfide
D) phosphine
E) dimethylmercury

Question 47

Which of the following is assimilated almost entirely in the oxidized state?

A) sulfur
B) nitrogen
C) phosphate
D) carbon
E) none of the above

Question 48

Compare and contrast the burning of fossil fuels in modern times with the rise of ancient cyanobacteria on atmospheric and planetary conditions.

Question 49

Anaerobically, H₂S may be photolyzed to:

A) sulfate
B) sulfite
C) sulfur dioxide
D) sulfuric acid
E) sulfur

Question 50

Household septic systems include a tank that collects sludge and a porous leaching field that receives clarified effluent. How is this similar to or different from municipal wastewater treatment plants?

Question 51

Which reservoir of carbon, nitrogen, and sulfur has the highest rate of cycling? Why is this so?

Question 52

How are wetlands similar to or different from commercial wastewater treatment plants?

Question 53

On which of the following planets does humankind expect to find life because of the similarity of its geology to that of Earth?

A) Jupiter
B) Venus
C) Mars
D) Jupiter's moon Europa
E) Pluto

Question 54

Describe the difference between a source, sink, and reservoir of an element.

Question 55

Which of the following is used by bacteria for iron uptake?

A) ferrodoxin
B) protein A
C) hemoglobin
D) siderophores
E) lipoprotein

Question 56

Discuss the impact of deforestation on atmospheric carbon dioxide levels.

Question 57

Which of the following is a major concern regarding biogeochemical and industrial sources of atmospheric sulfur?

A) greenhouse effect
B) acid rain
C) ozone depletion
D) inhibition of photosynthesis
E) odor production

Question 58

Which of the following represents a common microbial adaptation to limiting phosphorous concentrations?

A) Modifications of membrane structure and composition
B) Modifications of protein structure and composition
C) Modifications of DNA structure and composition
D) Modifications of polysaccharide structure and composition
E) Modifications of the cell wall structure and composition

Question 59

Which of the following can readily assimilate Fe³⁺?

A) plants
B) bacteria
C) animals
D) fungi
E) protists

Question 60

Which of the following is the most limiting element in marine ecosystems?

A) iron
B) sulfur
C) carbon
D) phosphorous
E) hydrogen

Question 61

Some bacteria are responsible for degrading concrete. How do they accomplish this?

Question 62

An environmental location has been contaminated with a high concentration of selenium. Explain how bacteria could be used to remediate this site.

Question 63

Explain how the Mississippi River drainage into the Gulf of Mexico off the coast of Louisiana leads to a large dead zone.

Question 64

What types of evidence suggest the past existence of water on Mars?

Question 65

Discuss the concept of iron fertilization to remove excess CO₂ from the atmosphere. Who is the well-known musician supporting this research?

Question 66

Astrobiology is the study of life in the universe. Why might our rDNA probes NOT be appropriate to detect extraterrestrial life?

Question 67

Discuss how human activities have perturbed the nitrogen cycle.

Question 68

Nitrogen is a major element for life on Earth. Discuss some of the reasons for its versatile use.

Question 69

What evidence suggests that the biochemistry of life elsewhere would resemble that on Earth?

Question 70

What are two mechanisms used by marine organisms to adapt to the paucity of phosphorous supply?