Deck 28: Microbial Ecology

Question 1

It is estimated that the mass of bacteria and fungi in the top six inches of an acre of soil is

A) 2 tons.
B) 100 lbs.
C) 10 tons.
D) 500 lbs.
E) 2 kilograms.

Answer 1

A

Question 2

Streptomyces

A) may produce antibiotics.
B) may produce antivirals.
C) are typically found in the air.
D) are frequently transmitted by vectors.
E) will swarm together to form fruiting bodies.

Answer 2

E

Question 3

The region of the earth inhabited by living organisms is called the

A) biosphere.
B) niche.
C) ecosystem.
D) community.
E) environment.

Answer 3

A

Question 4

Geosmins are

A) a strain of Bacillus.
B) nitrogen-fixing bacteria.
C) metabolites that give soil its odor.
D) produced by Rhizobium.
E) metabolites that give soil its odor AND produced by Rhizobium. F) metabolites that give soil its odor AND produced by Bacillus.

Question 5

The term used to describe the interrelationship between the living and non-living environments in an area is called a(n)

A) group.
B) community.
C) ecosystem.
D) ecological niche.
E) habitat.

Question 6

The bacteria cultured from a soil sample typically represents

A) all the bacteria present in that sample.
B) a very small number of bacteria present in that soil.
C) all the metabolically active bacteria.
D) all the metabolically inactive bacteria.
E) most of the types of bacteria in that soil.

Question 7

Nutrient poor waters are described as being

A) hypoxic.
B) oligotrophic.
C) autotrophic.
D) eutrophic.
E) anoxic.

Question 8

The role that an organism plays in its environment is called its

A) role.
B) niche.
C) position.
D) ecosystem.
E) habit.

Question 9

The environment immediately surrounding an individual cell is called its

A) macroenvironment.
B) microenvironment.
C) microniche.
D) colony.
E) macrohabitat.

Question 10

The major effect of excess water in the soil is to

A) increase the level of oxygen.
B) lower the amount of oxygen.
C) reduce the pH.
D) increase the amount of nitrogen.
E) reduce the amount of carbon.

Question 11

Which group is composed of autotrophs?

A) Primary consumers
B) Secondary consumers
C) Decomposers
D) Rotters
E) Primary producers

Question 12

Bacteria survive adverse conditions by forming

A) zygotes.
B) capsules.
C) endospores.
D) glycocalyx.
E) capsules AND endospores.

Question 13

An early contributor to the understanding of nitrogen fixation was

A) Hooke.
B) Pasteur.
C) Winogradsky.
D) Beijerinck.
E) Lister.

Question 14

A microbial mat

A) is a form of biofilm.
B) is poorly organized.
C) contains only obligate anaerobes.
D) is constructed to prevent interactions between the various layers of microorganisms.
E) is a form of biofilm AND is poorly organized.

Question 15

The organic matter in soil is referred to as

A) mineral soil.
B) humus.
C) inorganic substance.
D) bedrock.
E) mulch.

Question 16

Eutrophic waters

A) are nutrient rich AND contain 3.5% salt.
B) may become hypoxic AND lack phosphate, nitrate, and iron.
C) lack phosphate, nitrate, and iron AND contain 3.5% salt.
D) contain 3.5% salt AND are alkaline.
E) are nutrient rich AND may become hypoxic.

Question 17

Which of the following soil organisms play a major role in decomposing plant matter?

A) bacteria AND fungi
B) bacteria AND viruses
C) fungi AND protozoa
D) protozoa AND viruses
E) viruses AND fungi

Question 18

Biofilms are likely to be found in environments

A) that are nutrient rich.
B) that are relatively warm.
C) with rapidly flowing water.
D) with low nutrients.
E) with abundant nutrients.

Question 19

The problem of not being able to cultivate most microorganisms has led to the use of

A) FISH.
B) microscopy with fluorescent dyes.
C) 16s rRNA analysis.
D) FISH and 16s rRNA analysis.
E) All of these methods help identify microorganisms in the environment.

Question 20

The practice of cells turning on the production of some enzymes and turning off others in response to a changing environment is called

A) compromise.
B) adaptation.
C) metabolism.
D) nutritional metabolism.
E) quorum sensing.

Question 21

The zone of soil that surrounds the roots and contains a variety of organic exudates is called the

A) mycorrhizae.
B) rootsphere.
C) rhizosphere.
D) geosmin.
E) biosphere.

Question 22

Atmospheric nitrogen is

A) used directly by plants.
B) used directly by animals.
C) turned into ammonia by microorganisms.
D) directly used to make carbohydrates.
E) converted into urea by bacteria.

Question 23

The organisms that convert carbon dioxide into organic matter are the

A) secondary consumers.
B) primary consumers.
C) producers.
D) decomposers.
E) secondary decomposers.

Question 24

Next to carbon and oxygen, the element organisms most require is

A) sulfur.
B) phosphorus.
C) iron.
D) potassium.
E) nitrogen.

Question 25

The sulfur cycle is similar to the cycle of

A) carbon.
B) oxygen.
C) phosphorus.
D) water.
E) nitrogen.

Question 26

During anaerobic decomposition of organic matter with carbon dioxide as the terminal electron acceptor, the primary gas(es) produced is/are

A) oxygen.
B) hydrogen sulfide.
C) methane.
D) hydrogen.
E) methane AND hydrogen.

Question 27

The nitrogen in our atmosphere is only usable to us after it is converted to

A) ammonia.
B) amino acids.
C) fertilizer.
D) nitrous oxide.
E) oxygen.

Question 28

The carbon cycle revolves around

A) nitrogen.
B) carbon dioxide.
C) water.
D) phosphorus.
E) carbon monoxide

Question 29

Azotobacter

A) are the chief suppliers of fixed nitrogen in grasslands.
B) form symbiotic associations with algae.
C) have a very low respiratory rate.
D) are methanogens.
E) are the chief suppliers of fixed nitrogen in grasslands AND form symbiotic associations with algae.

Question 30

Turning inorganic carbon into organic carbon is called

A) mineralization.
B) eutrophication.
C) respiration.
D) carbon fixation.
E) carbonation.

Question 31

Nitrogen is

A) an important constituent of carbohydrates AND primarily fixed by fungi.
B) turned into ammonia by microorganisms AND ultimately used in making amino acids and nucleotides.
C) primarily fixed by fungi AND ultimately used in making amino acids and nucleotides.
D) ultimately used in making amino acids and nucleotides AND an important constituent of carbohydrates.
E) turned into ammonia by microorganisms AND ultimately used in making bacterial capsules.

Question 32

The organisms that obtain energy by oxidation of hydrogen sulfide and use carbon dioxide as a carbon source are called

A) heterotrophs.
B) chemolithoautotrophs.
C) chemoheterotrophs.
D) autotrophs.
E) chemoliths.

Question 33

The organisms isolated from hydrothermal vents are typically

A) phototrophs.
B) chemolithoautotrophs.
C) rhizobia.
D) bacteroid.
E) phototrophs, rhizobia, AND bacteroid.

Question 34

Which of the following may be used by prokaryotes, under anaerobic conditions, as terminal electron acceptors?

A) nitrate
B) nitrite
C) sulfate
D) carbon dioxide
E) All of the choices are correct.

Question 35

Sulfur occurs in all living matter primarily as a component of

A) fatty acids.
B) nucleotides.
C) amino acids.
D) carbohydrates.
E) DNA and RNA.

Question 36

Nitrifiers

A) are obligate anaerobes.
B) are chemolithotrophs.
C) convert nitrate to nitrite.
D) are reducers.
E) are thermophiles.

Question 37

During aerobic decomposition of organic matter the primary gas produced is

A) oxygen.
B) hydrogen sulfide.
C) nitrogen.
D) carbon dioxide.
E) ethylene dioxide.

Question 38

In many aquatic habitats, the growth of algae and cyanobacteria is limited by the amount of

A) nitrogen.
B) phosphorus.
C) calcium.
D) sulfur.
E) nitrites.

Question 39

Phosphorus is a component of all of the following EXCEPT

A) RNA and DNA.
B) phospholipids.
C) nucleotides.
D) carbohydrates.
E) ATP.

Question 40

The conical sea floor vents that spout sulfide-rich, super-heated water at temperatures up to 300ºC are called

A) hydrothermal vents.
B) yellow smokers.
C) warm vents.
D) hot vents.
E) hyperthermophiles.

Question 41

A mycorrhiza is a symbiotic association between roots and fungi.

Question 42

Fungi are able to handle acidic environments much better than bacteria.

Question 43

Gardeners sometimes plant clover between productive growing seasons. Why would this practice be beneficial?

A) Several types of nitrogen-fixing bacteria form a symbiotic relationship with the roots of clover. This would increase the amount of nitrogen in the soil available for subsequent seasons of other plants' growth.
B) Clover is consumed by a number of animals. This would encourage the animals to feed/graze on the areas, leaving behind nitrogen-rich manure (feces) that would act as a natural fertilizer for subsequent seasons of other plants' growth.
C) Clover is a unique plant that is capable of atmospheric nitrogen-fixation (pulling nitrogen directly out of the air and turning it into ammonia or amino acids). This directly provides nitrogen compounds for the soil for subsequent seasons of other plants' growth.
D) The beneficial effect is more for water retention and elimination of soil erosion in between growing seasons than for any nutrient value. It has nothing to do with nitrogen compounds in the soil.
E) Several types of oxygen-fixing bacteria form a symbiotic relationship with the roots of clover. This would increase the amount of oxygen in the soil available for subsequent seasons of other plants' growth.

Question 44

How do bacteriocins benefit bacteria in their natural habitat?

A) They protect the bacteria from the effects of antibiotics in the environment.
B) They provide a source of nutrients during adverse environmental conditions.
C) They allow bacteria to compete against other bacteria that may attempt to use the same or similar resources.
D) They are protective structures that allow bacteria to survive adverse environmental conditions.
E) They induce resistance in the bacteria, helping them survive when medications are introduced into their habitat.

Question 45

Explain how nutrient-rich runoff can cause waters to become hypoxic.

A) Algae and cyanobacteria flourish on the nutrients in the runoff. Heterotrophic microbes then flourish on the organic molecules produced by these organisms, using oxygen in the process and leading to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
B) Algae and cyanobacteria flourish on the nutrients in the runoff, using oxygen in the process. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
C) The nutrients in the runoff often include chemicals that spontaneously oxidize in the presence of oxygen. They tend to deplete the amount of oxygen present in an area simply by being present themselves. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
D) The nutrients in the runoff often include toxic chemicals that kill anaerobes such as cyanobacteria. Aerobes flourish, depleting the amount of oxygen present. This consumption of oxygen leads to a hypoxic state in the area. Larger animals cannot survive in the hypoxic area.
E) It doesn't. This claim is a scare tactic used by environmental extremists to prevent farmers and individuals from fertilizing their crops and lawns. There is no induction of a hypoxic state in bodies of water where runoff occurs.

Question 46

Bacteria are the most numerous soil inhabitants, but the biomass of fungi is greater.

Question 47

The organisms found near warm vents on the bottom of the ocean are typically chemoautotrophic.

Question 48

Which of the following refers to a symbiotic association between plant roots and fungi?

A) Lichens
B) Geosmins
C) Extremophiles
D) Ant gardens
E) Mycorrhizae

Question 49

Protozoa, algae, and fungus are typically found near the surface of soil.

Question 50

Mycorrhizae are a symbiotic association of

A) bacteria and algae.
B) plant roots and fungi.
C) bacteria and virus.
D) fungi and virus.
E) plants roots and bacteria.

Question 51

No eukaryotic organisms have been shown to fix nitrogen without the aid of prokaryotes.

Question 52

Which statement describes the relationship between ammonia oxidizers and nitrite oxidizers?

A) Ammonium oxidizers use ammonium as an energy source, oxidizing it to nitrite. The nitrite produced then serves as the energy source for nitrite oxidizers.
B) Ammonium oxidizers use ammonium as an energy source, oxidizing it to nitrate. The nitrate produced then serves as the energy source for nitrite oxidizers.
C) Ammonium oxidizers use urea as an energy source, oxidizing it to nitrite. The nitrite produced then serves as the carbon source for nitrite oxidizers.
D) Ammonium oxidizers use ammonium as an energy source, reducing it to nitrate. The nitrate produced then serves as the energy source for nitrite oxidizers.
E) None of these explains the relationship-ammonia and nitrite are produced by different nutrient cycles which also involve sulfur reduction.

Question 53

Which of the following involve symbiotic relationships?

A) rhizobia AND ruminants
B) mycorrhizae AND ruminants
C) ruminants AND myxobacteria
D) myxobacteria, ruminants, AND rhizobia
E) rhizobia, mycorrhizae, AND ruminants

Question 54

Streptomyces produces geosmins which give soil a characteristic musty odor.

Question 55

How can the biomass of fungi in soil be greater than that of bacteria, considering that bacteria are more numerous?

A) Fungi are always multicellular organisms, while bacteria are unicellular. As such, biomass of fungi would always be larger than that of bacteria, since they possess more cells in each individual organism.
B) This is a matter of size. Fungi, whether unicellular or multicellular, are eukaryotic and are generally larger than bacteria (which are prokaryotic). This means that, even with a lower overall number, they will have more total biomass.
C) It depends on where they grow. Fungi generally grow in the most moist areas near the top of soil, giving them an advantage over bacteria. They may not be as numerous, but this advantage in location and nutrients is what makes them larger than the bacteria (and therefore having more biomass). 
D) Fungi are capable of incorporating the dead materials around them into themselves as nutrient sources. This capacity allows them to greatly increase their biomass per each organism, well beyond what a simple bacterial cell could hold. This capability is what allows them to achieve higher biomass than bacteria.
E) Bacteria may be more numerous, but in soil they exist mostly in a dehydrated state. Because they lack moisture, they weigh less than fungi, which may occur in lower numbers but are heavier because they are well hydrated in all soil environments.

Question 56

Many orchids require fungi for seeds to germinate.

Question 57

Sulfur occurs in all living matter primarily as a component of carbohydrates.

Question 58

Oligotrophic waters are usually hypoxic.

Question 59

Truffles

A) are endomycorrhizas.
B) are a mushroom.
C) are a lichen.
D) form a sheath around a root of an appropriate tree.
E) are endomycorrhizas AND form a sheath around a root of an appropriate tree.

Question 60

The rumen is

A) found in horses and rabbits.
B) an anaerobic fermentation vessel found in herbivores.
C) found in carnivores.
D) an offshoot of the colon.
E) an anaerobic fermentation vessel found in most carnivores.

Question 61

What gene sequences are used to identify the prokaryote organisms present in an environmental sample?

A) 18S rRNA genes
B) 16S rRNA genes
C) 70S rRNA genes
D) 80S rRNA genes
E) All of these

Question 62

Please select the correct sequence of steps involved in the creation of a dead zone in a water body.
1) Heterotrophic microbes metabolize the organic compounds synthesized by primary producers.
2) Water becomes hypoxic and toxic algal blooms may occur; animals in the area either flee or die.
3) Water accumulates nutrients as it runs through agricultural, industrial, and urbanized regions.
4) Dissolved O₂ is consumed by metabolic activity of heterotrophs.
5) Excess nitrate and phosphate in nutrient-rich water causes algae and cyanobacteria to flourish.

A) 3; 5; 1; 4; 2
B) 3; 1; 4; 2; 5
C) 1; 3; 4; 2; 5
D) 5; 3; 4; 2; 1
E) 2; 1; 4; 3; 5

Question 63

What is the likely fate of a fish living in a eutrophic stream?

A) Fish will first thrive as they have more oxygen from the increase in photosynthetic organisms; eutrophic streams are low in nutrients however, so they will quickly die.
B) Eutrophic streams have high levels of carbon dioxide. Fish will be able to use this for aerobic respiration, so will thrive in this environment.
C) Eutrophic streams are always anoxic. This means that only anaerobic fish will be able to survive in a eutrophic environment.
D) Fish will first thrive as they have more food from the increase in photosynthetic organisms; as they deplete the dissolved oxygen, however, they will die. 
E) Eutrophic streams have low levels of nutrients in them. Only fish that feed off other fish will be able to survive in these streams.

Question 64

Which of the following statements regarding microbial identification is False?

A) FISH can be used to distinguish subsets of prokaryotes that contain a specific nucleotide sequence.
B) Studying the genome of one organism can give insights into the characteristics of another organism.
C) 16S rRNA sequences can be used to determine taxonomic similarity among prokaryotes.
D) Metagenomics involves comparison of gene sequences in DNA from environmental samples to known gene sequences in databases.
E) Culture techniques are an accurate way of determining which members in a microbial community are most common.

Question 65

Which of the following is not a matching pair?

A) Soil-minimal biodiversity
B) Bacillus-endospores
C) Streptomyces-geosmin production
D) Fungi-lignin degradation
E) Rhizosphere-soil that adheres to plant root