Microbiology Chapter 15: Microbial ecosystems

What is the best classification of primary producers found in hydrothermal vents on the ocean bottom?

a) photosynthetic

b) organotrophs

c) chemolithoautotrophs

d) chemoorganoheterotrophs

e) photolithoautotrophs

c) chemolithoautotrophs

Microbes are able to generate energy through the:

a) oxidation of organic compounds only.

b) reduction of organic compounds only.

c) oxidation of inorganic and organic compounds.

d) reduction of inorganic and organic compounds.

e) synthesis of ATP.

c) oxidation of inorganic and organic compounds.

Which of these is NOT an advantage of living in a biofilm community?

a) protection from predation

b) water availability

c) protection from toxins

d) nutrient availability

e) genetic exchange

b) water availability

Which of these is the LEAST important physiological activity to consider when studying an eco-system?

a) primary production by chemolithotrophs

b) primary production by phototrophs

c) decomposition by chemoorganotrophs

d) methane production by methanogens

e) biogeochemical cycling of the elements

d) methane production by methanogens

Which of these regulates the formation of biofilms?

a) photosynthesis

b) quorum sensing

c) water availability

d) catabolite repression

e) end product repression

b) quorum sensing

Today, the most effective technique for analyzing microbial community structure is based on this analysis.

a) Sequencing small subunit rRNA.

b) Identification of the catabolic enzymes present.

c) Isolation and characterization of microbes from the community.

d) Enrichment culture technique for microbial isolation.

e) Identification of metabolic intermediates that accumulate in the environment.

a) Sequencing small subunit rRNA.

In the microbial world, an "operational taxonomic unit" is defined as any group of microbes that share at least __________ sequence identity of their SSU gene.

a) 100%

b) 97%

c) 90%

d) 80%

e) 50%

b) 97%

FISH is a fluorescent microscopic technique used to differentiate microbes using this fluores-cently labeled material.

a) antibody

b) antigen

c) protein

d) DNA probe

e) lipid

d) DNA probe

What is the estimated percentage of microbial species on Earth have been grown in culture?

a) 1 -5%

b) 5 - 10 %

c) 10 - 15%

d) 15-20%

e) 20 - 25%

a) 1 -5%

Which of these represents MOST of the ocean's biomass?

a) fish

b) sea mammals

c) fish and sea mammals

d) marine plants

e) microbes

e) microbes

What is the % salinity of the ocean?

a) 1% or less

b) 3.5%

c) 8%

d) 15%

e) 35%

b) 3.5%

Which elements necessary for microbial life are often limiting in the ocean?

a) magnesium and calcium

b) nitrogen and phosphorous

c) magnesium and chloride

d) sodium and calcium

e) potassium and magnesium

b) nitrogen and phosphorous

Which of these characterizes dead zones in the ocean?

a) Low temperatures.

b) Lacking microbial life.

c) Being hypoxic.

d) Being oligotrophic.

e) Lacking nutrients.

c) Being hypoxic.

What is the average temperature of the world's ocean waters?

a) 2 to 3°C

b) 8 to 10°C

c) 12 to 15°C

d) 18 to 20°C

e) 22 to 25°C

a) 2 to 3°C

The coastal marine waters contain on average about _________ microbial cells per ml.

a) 10

b) 100

c) 10,000

d) 1 million

e) 100 million

e) 100 million

Which of the following groups is the most abundant in the ocean?

a) viruses

b) fungi

c) phytoplankton

d) Bacteria

e) Eukarya

a) viruses

Which of these best summarizes the contribution of cyanobacteria in the open ocean?

a) primary carbon production

b) oxygenation of the waters

c) nitrogen fixation

d) primary carbon production and oxygenation of the waters

e) primary carbon production, oxygenation of the waters, and nitrogen fixation

e) primary carbon production, oxygenation of the waters, and nitrogen fixation

Approximately what percent of primary production reaches the ocean floor?

a) one

b) five

c) ten

d) twenty

e) forty

a)one

To grow the widest diversity of marine microbes from the open ocean requires growth media that contain which of the following?

a) High amounts of various organics.

b) High amounts of carbohydrates.

c) High amounts of proteins.

d) Very low carbon concentrations.

e) Very low amounts of proteins and high amounts of carbohydrates.

d) Very low carbon concentrations.

How would you best classify most of the microbes from marine environments that cannot be isolated?

a) obligate anaerobes

b) obligate oligotrophs

c) obligate acidophiles

d) extreme halophiles

e) extreme thermophiles

b) obligate oligotrophs

Proteorhodopsin has been found in many marine bacteria, including the SAR-11 group. What is this protein's function?

a) In the digestion of proteins.

b) As a light-driven proton pump.

c) As a photosynthetic reaction center.

d) As a repressor for global regulation.

e) As an activator for global regulation.

b) As a light-driven proton pump.

In terrestrial environments, where is the greatest microbial diversity found?

a) lakes

b) rivers and streams

c) soil

d) rocks

e) springs

c) soil

Soil texture classification is based on the percent of __________ that make up the soil.

a) air, water, and solids

b) water and solids

c) sand, silt, and clay

d) sand and water

e) clay and sand

c) sand, silt, and clay

Most of the organic matter in soil comes from the decomposition of what material?

a) animals

b) plants

c) fungi

d) protozoa

e) algae

b) plants

Where is the soil's rhizosphere?

a) Areas in contact with bodies of water.

b) Areas in direct contact with the atmosphere.

c) Areas surrounding plant roots.

d) Patches that support nitrogen fixation.

e) Zones that contain animal life.

c) Areas surrounding plant roots.

Soil microbes surrounding the plant root contribute to plant growth by providing the plants with all of the following EXCEPT:

a) a source of fixed nitrogen.

b) soluble phosphorus.

c) water.

d) a usable carbon source.

e) protection from pathogens

d) a usable carbon source.

Lignocellulose is primarily mineralized by this group of organisms during plant decomposition.

a) fungi

b) Gram positive bacteria

c) Gram negative bacteria

d) Archaea

e) slime molds

a) fungi

What are humic substances?

a) clay particles

b) recalcitrant organic molecules

c) glucose molecules

d) carbonates and phosphates

e) silt and sand

b) recalcitrant organic molecules

All of the following but one are xenobiotics that frequently contaminate our terrestrial environ-ments. Which one does NOT represent a xenobiotic?

a) polychlorinated biphenyls

b) polycyclic aromatics

c) lignin

d) trichloroethylene

e) nitroaromatics

c) lignin

Which of these pairs best categorizes water below the thermocline in a lake during the summer?

a) warm and aerobic

b) low density and anaerobic

c) cold and aerobic

d) low density and aerobic

e) cold and anaerobic

e) cold and anaerobic

) From the study of deep subsurface microbiology, what is the approximate upper temperature limit for microbial growth?

a) 80°C

b) 90°C

c) 100°C

d) 110°C

e) 120°C

e) 120°C

What is the deepest that viable microorganisms have been found in the Earth's crust?

a) 100 meters

b) 500 meters

c) 1000 meters

d) 1500 meters

e) 3000 meters

e) 3000 meters

What possible sources of energy may be used by microbes that live deep within the Earth?

a) carbon dioxide and oxygen

b) hydrogen gas and ferrous iron

c) nitrate and sulfate

d) sulfate and ferric iron

e) nitrate and ferric iron

b) hydrogen gas and ferrous iron

What possible sources of energy may be used by microbes living in hydrothermal vents?

a) nitrate and methane

b) methane and sulfide

c) sulfide and nitrate

d) sulfate and nitrate

e) sulfate and methane

b) methane and sulfide

Moderate temperature and neutral pH geothermal springs in terrestrial environments may contain __________ as primary producers.

a) chemolithotrophs

b) oxygenic phototrophs

c) anoxygenic phototrophs

d) oxygenic and anoxygenic phototrophs

e) oxygenic and anoxygenic phototrophs and chemolithotrophs

d) oxygenic and anoxygenic phototrophs

Microbes can form a biofilm on any type of surface.

true

Biofilms in the environment are usually comprised of a single species.

false

Most of the ocean is oligotrophic or nutrient poor.

true

Estimates of overall microbial abundance in the ocean indicate that more Archaea are present than Bacteria.

true

The greatest diversity of microbial life in a terrestrial environment is found in lakes.

false

Deep subsurface environment are considered to be void of microbial life

false

A community of organisms living in a specified area that are interacting with each other and their environment is called a(n) ________________.

ecosystem

The specific function role of an organism in an ecosystem is called the ___________.

niche

The part of the soil that immediately surrounds the plant root is called the __________.

rizosphere

The use of living organisms to clean up chemically contaminated soils is called __________.

bioremediation

The depth of a stratified lake that is characterized by a rapid decrease in temperature and oxygen is called the ________________

thermocline

Sulfur emitted from hydrothermal vents is in the form of __________.

sulfide

Briefly describe the formation of a biofilm.

The initiation of biofilm formation starts with the reversible attachment of a microorganism to a solid surface. The attachment may be mediated through fimbriae, a flagellum, or other append-ages. If the microbe initiates formation of a capsule or slime layer, then attachment may become permanent. After permanent attachment the microbe will begin to grow and divide, producing a microcolony. Other microbes will also begin to attach to the forming biofilm matrix, and will start to communicate with one another through a quorum sensing mechanism to enhance biofilm formation. Quorum sensing will regulate gene expression for optimal biofilm formation and mat-uration.

Describe how FISH is used to detect certain groups of microorganisms

FISH (Fluorescent in-situ hybridization) is a fluorescent microscopy technique used to detect specific microbes in the environment. The technique uses a fluorescently-labeled DNA probe for either the detection of a specific gene or the expression of a specific gene in a cell. For example, a DNA-probe can be used to detect a specific metabolic activity such as nitrification. Nitrifying bacteria can be identified by this method using a probe that specifically binds to the nitrite oxidase gene.

Describe the beneficial relationship that exists between plants and microorganisms.

Plants attract microbes to the plant root through the excretion of root exudates, comprised of sugars, organic acids, and sugar alcohols, which can be readily used by microorganisms as sources of carbon and energy. Microbes provide the plant with a source of soluble phosphates, water, protection from harmful microbes, and a useable form of nitrogen.