Deck 15: Functional Diversity of Microorganisms

Question 1

Typical electron donors used by dissimilative sulfate-reducers are

A) hydrogen, water, and hyrdrogen sulfide.
B) hydrogen, lactate, and pyruvate.
C) carbon dioxide, hydrogen, and water.
D) sulfate, sulfur, and thiosulfate.

Answer 1

B

Question 2

The phylogenetic trees of the nifH and SSU rRNA genes of nitrogen-fixing bacteria are incongruent because

A) nitrogenase is an anaerobic enzyme.
B) this is a characteristic of all enzyme genes.
C) of horizontal gene transfer.
D) very few microbes have the nifH gene.

Answer 2

C

Question 3

Microbial diversity is thought of in terms of phylogenetic diversity and functional diversity because

A) similar functional traits are often found in divergent phylogenetic groups.
B) phylogenetic diversity dictates functional diversity in microbes.
C) functional diversity only pertains to functions that are not phylogenetic.
D) similar phylogenetic groups almost always have similar functional traits.

Answer 3

A

Question 4

The only group of oxygenic phototrophic bacteria are the

A) green nonsulfur bacteria.
B) Chloroflexi.
C) Cyanobacteria.
D) Chlorobi.

Question 5

Considering the relationship between oxidizers and reducers, which of the following pairs of microorganisms are NOT likely to form close associations or consortia?

A) purple sulfur bacteria and dissimilative sulfur-reducers
B) dissimilative sulfur-reducers and dissimilative sulfur-oxidizers
C) diazotrophs and fungi
D) nitrogen-fixing cyanobacteria and dissimilative sulfate-reducers

Question 6

The vacuole of the giant sulfide-oxidizing bacterium Thiomargarita namibiensis contains ________ that is used to oxidize hydrogen sulfide under ________ conditions.

A) nitrate / anoxic
B) sulfate / anoxic
C) oxygen / oxic
D) sulfur / anoxic

Question 7

Which of the following conditions would you use to enrich purple nonsulfur bacteria from lake sediments?

A) anoxic media with a good light source
B) mineral media with ammonia and oxygen in the dark
C) anoxic mineral media with an organic acid and a good light source
D) mineral media with nitrate and acetate in the dark

Question 8

What form of photosynthesis evolved first on Earth?

A) oxygenic
B) anoxygenic
C) autotrophic
D) heterotrophic

Question 9

All microbial phototrophs

A) fix carbon dioxide.
B) use water as an electron donor for photosynthesis.
C) fix carbon dioxide and use water as an electron donor for photosynthesis.
D) use light energy to drive electron transport to generate energy.

Question 10

The ecological diversity of phototrophic bacteria is illustrated by the different ________ that allow them to perform photosynthesis in low light environments such as deep in the ocean, in various sediments, and in thick layered mats.

A) nitrogen fixation strategies
B) bacteriochlorophyll and photosystems
C) specialized stalked cells
D) endospores and resistant cell types

Question 11

Sulfate-reducing bacteria are a ________ that are found in ________ environments.

A) monophyletic group / anoxic
B) polyphyletic group / oxic
C) morphologically distinct group / anoxic
D) morphologically distinct group / oxic

Question 12

The Cyanobacteria are united by their ________, but their ________ is very diverse.

A) physiology / morphology
B) morphology / physiology
C) ecology / physiology
D) SSU rRNA gene sequences / physiology

Question 13

Aside from using light as a source of energy, another important part of the functional diversity of some bacterial phototrophs is their ability to

A) bioluminesce.
B) form prosthecate and stalked cells.
C) fix nitrogen gas.
D) degrade neurotoxins.

Question 14

Functional traits can be shared between organisms with divergent SSU rRNA gene sequences because

A) functional traits may be lost by different lineages over time.
B) functional traits may evolve independently in different lineages over time.
C) horizontal gene transfer can result in the transfer of genes between divergent lineages.
D) functional traits may evolve independently, be shared through horizontal gene transfer, or be lost in divergent lineages.

Question 15

You are looking at a sample from the top green layer of a colorful bacterial mat. Using phase contrast and fluorescence microscopy, you see evenly spaced cells in the middle of a filament that are slightly smaller than the others. The smaller cells are not fluorescent, indicating they lack photosystem II, but the rest of the filament is fluorescent. What type of filamentous bacteria are you most likely looking at?

A) purple nonsulfur bacteria
B) green sulfur bacteria
C) Acidobacteria
D) Cyanobacteria

Question 16

Purple sulfur bacteria are

A) alphaproteobacteria that oxidize hydrogen sulfide in the presence of oxygen or nitrate.
B) gammaproteobacteria that use hydrogen sulfide as an electron donor for photosynthesis.
C) a phylogenetically heterogeneous group of microbes that reduce sulfate to sulfur.
D) thermophilic bacteria that reduce elemental sulfur to sulfide.

Question 17

Which group of bacteria would you expect to find in a shallow clear hot spring with high concentrations of geochemically produced hydrogen sulfide?

A) purple sulfur bacteria
B) single-celled Cyanobacteria
C) dissimulative sulfate-reducing bacteria
D) symbiotic diazotrophs

Question 18

Aerobic anoxygenic phototrophs

A) do not use bacteriochlorophyll.
B) are an ancient monophyletic group of bacteria.
C) can be either autotrophic or heterotrophic.
D) cannot fix CO₂.

Question 19

You are looking at a sample from the top green layer of a colorful bacterial mat. Using phase contrast and fluorescence microscopy, you see evenly spaced cells in the middle of a filament that are slightly smaller than the others. The smaller cells are not fluorescent, indicating they lack photosystem II, but the rest of the filament is fluorescent. What is the most likely function of the smaller cells in the filament?

A) survival in the dark
B) nitrogen fixation
C) sulfur storage
D) nitrate storage

Question 20

Nitrogen fixation is

A) rare among microorganisms.
B) widespread among microorganisms.
C) limited to Proteobacteria.
D) common in Bacteria, but absent in Archaea.

Question 21

Most methanotrophs are obligate ________ because ________.

A) aerobes / the initial step of methane oxidation requires O₂
B) anaerobes / methane is produced in anaerobic environments
C) fermenters / methane only provides enough energy for fermentation
D) heterotrophs / methane does not provide enough carbon for growth

Question 22

Nitrogenase is a critical enzyme in the nitrogen cycle because it catalyzes the

A) assimilation of ammonia.
B) dissimilative reduction of nitrate to nitrogen gas.
C) fixation of nitrogen gas into ammonia.
D) oxidation of nitrogen gas into nitrate.

Question 23

Which of the following functional groups form symbiotic relationships with Eukaryotes in deep sea environments?

A) dissimilatory iron-oxidizers
B) methanotrophs
C) sulfide-oxidizers
D) methanotrophs and sulfide-oxidizers

Question 24

Bdellovibrio species are ________ cells that replicate in the ________.

A) symbiotic / gills of clams
B) lithotrophic / deep subsurface
C) predatory / periplasmic space
D) denitrifying / sediments of freshwater lakes

Question 25

Green sulfur bacteria are often found at the greatest depths of all phototrophic cells in lakes, oceans, and microbial mats. This is because green sulfur bacteria

A) are very sensitive to UV irradiation, despite their reliance on light for energy.
B) are the only phototrophs that can use hydrogen sulfide as an electron donor for photosynthesis.
C) are strict anaerobes.
D) have chlorosomes that are very efficient at harvesting light, allowing them to perform photosynthesis where light intensities are very low.

Question 26

Diazotrophs maximize nitrogenase activity by

A) closely coupling N₂ fixation with high rates of photosynthesis.
B) fixing N₂ at times when oxygen is absent or in low concentrations.
C) producing specialized structures to protect nitrogenase from oxygen.
D) producing specialized structures or fixing N₂ at times when oxygen is absent to protect nitrogenase from oxygen.

Question 27

Dissimilative iron-reducing bacteria couple which oxidation-reduction reactions?

A) The reduction of ferric iron or manganese and the oxidation of sulfur.
B) The reduction of ferric iron or manganese and the fermentation of sugars.
C) The oxidation of H₂ or organic compounds and the reduction of ferric iron or manganese.
D) The reduction of ferric iron and photosynthesis.

Question 28

What growth conditions would you use to enrich for ammonia-oxidizing bacteria?

A) aerobic mineral media with ammonia and bicarbonate incubated in the dark
B) anaerobic mineral media with acetate and ammonia incubated in the dark
C) aerobic mineral media with acetate and ammonia incubated in the dark
D) anaerobic mineral media with ammonia and nitrate incubated in the dark

Question 29

Epibiotic predators

A) obtain nutrients by attaching to the surface of prey.
B) invade the cytoplasm of their prey.
C) invade the periplasmic space of their prey.
D) find prey using swarming behavior.

Question 30

What microbes have a symbiotic association with mussels, living in their gill tissue?

A) methanotrophs
B) iron-oxidizing bacteria
C) bioluminescent bacteria
D) sulfur oxidizing bacteria

Question 31

What is the difference between a methylotroph and methanotroph?

A) Methylotrophs are strict anaerobes, while methanotrophs are strict aerobes.
B) Methylotrophs use organic carbon lacking C-C bonds as electron donors and carbon sources, while methanotrophs exclusively use methane as an electron donor and carbon source.
C) Methylotrophs produce organic carbon lacking C-C bonds, while methanotrophs exclusively produce methane.
D) Methylotrophs are in Proteobacteria, while methanotrophs are in Archaea.

Question 32

Which of the following functional groups would you expect to find in aerobic iron- and sulfur-rich acidic mine drainage?

A) dissimilative iron-oxidizers
B) dissimilative iron-reducers
C) purple sulfur bacteria
D) purple sulfur bacteria and dissimilative iron-reducers

Question 33

Thioploca species contain large vacuoles that store ________, which is used to ________ under anaerobic conditions.

A) nitrate / oxidize sulfide
B) oxygen / oxidize sulfur
C) sulfur / reduce nitrate
D) glycogen / provide energy

Question 34

In symbiotic associations between sulfur chemolithotrophs and eukaryotes such as tube worms and giant clams, the bacterial symbiont provides ________ while the host provides ________.

A) nitrogen / carbon and oxygen
B) sulfide / oxygen
C) a carbon and energy source / stable sulfide and oxygen levels
D) organic acids / stable sulfate levels

Question 35

The Bacteria and Archaea are the ONLY domains in which organisms exist that can

A) catalyze the transformation of inorganic nitrogen species for biosynthesis.
B) assimilate nitrite.
C) conserve energy from the transformation of inorganic nitrogen species.
D) catalyze the incorporation of inorganic nitrogen species into biomolecules.

Question 36

What is one especially unique characteristic of methanotrophs?

A) They metabolize H2S.
B) They have unusually large amounts of sterols.
C) They can exist as consortia.
D) They are capable of bioluminescence.

Question 37

Dissimilatory sulfide-oxidizers use a variety of unique ecological strategies in order to

A) avoid the toxicity of hydrogen sulfide.
B) position themselves at interfaces where sulfide and oxygen meet.
C) position themselves where there is sufficient light for sulfide oxidation.
D) find organic carbon substrates.

Question 38

In which of the following environments would you expect to find a high number of iron-reducing bacteria?

A) acidic mine drainage
B) deep subsurface
C) open ocean
D) agriculture soil

Question 39

Escherichia coli is a chemoorganotrophic, facultative aerobe and belongs to the phylum Proteobacteria. Based on this information, which of the following functional groups does E. coli most likely belong to?

A) green sulfur bacteria
B) ammonia-oxidizing bacteria
C) denitrifying bacteria
D) nitrite-oxidizing bacteria

Question 40

Which of the following traits do ammonia and nitrite oxidizers share?

A) chemoorganotrophic
B) autotrophic
C) aerobic
D) autotrophic and aerobic

Question 41

Bioluminescent microorganisms are found in which of the following groups?

A) Firmicutes
B) Thaumarchaeota
C) Gammaproteobacteria
D) Verrucomicrobia

Question 42

Bioluminescence is controlled by the gene regulatory mechanism called quorum sensing, wherein the

A) depletion of oxygen is detected by an inducer molecule which activates transcription of the lux operon (genes luxCDABE).
B) accumulation of an inducer molecule activates transcription of the lux operon (genes luxCDABE).
C) absence of light activates an inducer molecule which activates transcription of the lux operon (genes luxCDABE).
D) host tissues produce an autoinducer molecule which activates transcription of the lux operon (genes luxCDABE).

Question 43

Prosthecae are an adaptation for

A) anaerobic growth.
B) cell differentiation under harsh conditions.
C) nitrogen fixation.
D) low nutrient aquatic environments.

Question 44

Unicellular cyanobacteria are the most abundant phototrophs in the ocean and perform 80% of marine photosynthesis.

Question 45

Dissimilatory nitrate reduction results in the production of gaseous products, while assimilatory nitrate reduction results in the production of ammonia for biosynthesis.

Question 46

Dissimilatory iron-oxidation is a relatively new metabolism and is restricted to one unusual phylum of bacteria.

Question 47

Iron-reducing bacteria are obligately aerobic organisms that reduce ferric iron and oxidize hydrogen or organic compounds.

Question 48

Bioluminescence develops when

A) population density is high.
B) oxygen is depleted.
C) ambient light is low.
D) the host induces the bioluminescence genes.

Question 49

Although Cyanobacteria contribute more than 35% of all photosynthesis on Earth, they are not visible in the natural environment.

Question 50

Nitrogenase is an oxygen-sensitive enzyme even though many diazotrophs are aerobic microorganisms.

Question 51

Bioluminescence is catalyzed by luciferase, which creates light by

A) shunting electrons from FMNH₂ to O₂, which releases energy in the form of light.
B) reversing photosynthesis, which produces a surplus of ATP.
C) hydrolyzing ATP to release the excess energy as light.
D) reducing LuxR, the regulatory protein that controls the lux operon.

Question 52

Diazotrophs are obligately symbiotic bacteria that fix N₂ into ammonia, thus providing a critical source of nitrogen to their host.

Question 53

The ecological diversity of microbes is largely dependent on their complex morphological and structural diversity.

Question 54

Anoxygenic phototrophs may or may not be autotrophs.

Question 55

Akinetes and hormogonia are specialized cells, found in some cyanobacteria, that facilitate nitrogen fixation.

Question 56

Diazotrophs are found in all three domains of life.

Question 57

Sulfide oxidizers are among the most ecologically diverse trophic groups because of the different strategies they employ to access sufficient amounts of sulfide and oxygen simultaneously.

Question 58

There are currently no known predatory bacteria that are adapted to invade or kill nearby cells.

Question 59

Denitrifying bacteria are often facultative anaerobes, capable of performing other forms of respiration or fermentation as well as nitrate reduction.

Question 60

Myxobacteria display ________ behavior and form ________ that produce myxospores.

A) gliding / slime trails
B) chemotactic / colonies
C) phototactic / slime trails
D) swarming / fruiting bodies

Question 61

Compare and contrast two different ecological strategies that sulfide-oxidizing bacteria use to access sulfide and oxygen.

Question 62

Bacteria that contain complex internal membrane systems are more likely to divide by budding than by binary fission.

Question 63

What is convergent evolution and how is it different from horizontal gene transfer?

Question 64

Prosthecae are thought to be an adaptation to growth in nutrient-rich environments such as sediments and sewage.

Question 65

Discuss the ecological importance of the enzyme nitrogenase, the diversity and physiology of the various groups of organisms that contain it, and the strategies these organisms use to optimize conditions for the enzyme.

Question 66

How do Cyanobacteria impact the ecology of both aquatic and terrestrial environments on Earth?

Question 67

Spirilla and spirochetes are closely related bacteria that exhibit a unique corkscrew motility.

Question 68

Budding bacteria form new cell wall material at a single point rather than throughout the whole cell.

Question 69

Design an enrichment strategy for the isolation of a heterotrophic sulfate-reducer that could help clean up the oil spill in the sediments of the Gulf of Mexico.

Question 70

Budding is a form of reproduction whereby prokaryotic microbes can reproduce sexually.

Question 71

All phototrophic bacteria use a monophyletic photosystem in photosynthesis, thus there is intense competition for light between different phototrophic bacteria.

Question 72

What functional group (or groups) of microbes would be most useful in a microbial fuel cell in which electrons are transferred to and from solid metal electrodes? Why?

Question 73

Bacteria and Archaea are general single-celled organisms, but some phyla form sheaths around multiple cells to facilitate attachment and filament formation.

Question 74

Thiobacillus species are acidophilic chemolithotrophs capable of autotrophic growth. They perform the dissimilative oxidation of H₂S, Sᵒ, thiosulfate, or Fe⁺². Diagram or explain how Thiobacillus species obtain carbon and energy for growth and predict what type of environment they would be found in.

Question 75

Tilling or plowing is a common agriculture practice that has been proven to have a profound impact on the nitrogen cycle. Tilling breaks up hard soils to ease the planting and germination of crops, and it also introduces more oxygen into the soil. Many fertilizers contain N in the form of ammonia because ammonia is readily absorbed and used by plants, while N in the form of nitrate is more mobile and is more easily lost from the soil. Based on your knowledge of microbial transformations of inorganic nitrogen species, what impact would you predict extensive tilling to have on the fate of ammonium-based nitrogen fertilizer?

Question 76

Bioluminescence is a social behavior of bacterial cells that causes luminescence to occur when a dense cell population has been attained.

Question 77

Given that multiple diverse phyla (e.g., diverse phylogenetic groups) of microorganisms can perform similar functions in ecosystems, how we might predict the microbial functions performed by a particular organism or in a particular environment without relying on growing all of the microbes in the lab?

Question 78

Based on the FUNCTIONAL characteristics of the Cyanobacteria and Proteobacteria phyla, which phylum do you think is more deeply rooted in the tree of life (i.e., which phylum branches off closer to the last universal common ancestor)? Use at least two pieces of evidence to support your answer. How could you test your hypothesis?

Question 79

Magnetosomes are specialized magnetic structures, found in iron-reducing bacteria, that aid in chemotaxis towards iron-oxides.

Question 80

Organisms that fix dinitrogen gas into ammonia are called diazotrophs.