Question 1

Microbes are able to generate energy through the:

Accepted Answer

Microbes are able to generate energy through both the oxidation of inorganic compounds (such as oxygen, nitrate, and sulfur) and organic compounds (such as sugars and fats). This process, known as cellular respiration, involves the transfer of electrons from high-energy molecules to an electron acceptor, which generates a proton gradient that can be used to synthesize ATP.

Question 2

Approximately what percent of primary production reaches the ocean floor?

Accepted Answer

Only about 1% of primary production makes it to the ocean floor as the majority of organic matter is consumed in the water column by zooplankton or decomposed by bacteria before it reaches the seafloor.

Question 3

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

Accepted Answer

Sequencing small subunit rRNA provides information on the genetic diversity of the microbial community and allows for identification of specific taxa present. This technique has become the standard for microbial community analysis.

Question 4

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

Accepted Answer

Marine environments are often oligotrophic, meaning they have low nutrient availability. Many microbes in these environments have adapted to these conditions and are specialized for obtaining nutrients from the limited resources available. As a result, they may not be able to grow in typical laboratory culturing conditions, making them difficult to isolate. Therefore, most of the microbes from marine environments that cannot be isolated can be classified as obligate oligotrophs.

Question 5

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

Accepted Answer

Microbes, specifically plankton, make up the majority of the ocean's biomass. They play a crucial role in the marine food web and are a primary source of food for larger marine animals such as fish and sea mammals.

Question 6

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

Accepted Answer

Nitrogen and phosphorous are essential elements for microbial life, but they are often limiting in the ocean due to their low availability. This is because they are largely present in particulate organic matter or dissolved organic matter, which are not easily accessible to microbes. Without sufficient nitrogen and phosphorous, microbial growth and metabolism can be restricted, ultimately affecting the entire marine food web.

Question 7

Which of these characterizes dead zones in the ocean?

Accepted Answer

Dead zones in the ocean are characterized by hypoxia, which means low oxygen levels. This is often caused by excessive nutrient pollution, leading to blooms of algae that consume all the available oxygen when they die and decompose.

Question 8

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

Accepted Answer

Cyanobacteria in the open ocean are responsible for primary carbon production through photosynthesis, which is a vital process for the marine food web. They also play a significant role in oxygenating the surface waters through photosynthesis. Additionally, they are known for their ability to fix nitrogen, which is essential for the growth of phytoplankton and other marine organisms. Therefore, the best choice is E, which summarizes all three contributions of cyanobacteria in the open ocean.

Question 9

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

Accepted Answer

Marine microbes from the open ocean are adapted to environments with low nutrient concentrations, so growth media with very low carbon concentrations are needed to mimic their natural conditions and support their growth.

Question 10

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

Accepted Answer

The answer of What is the average temperature of the...

Question 11

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

Accepted Answer

It is estimated that only 1-5% of microbial species on Earth have been successfully grown in culture. This means that the vast majority of microbial life remains unknown and uncharacterized.

Question 12

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

Accepted Answer

Primary producers found in hydrothermal vents on the ocean bottom are typically chemolithoautotrophs, which use inorganic compounds such as hydrogen sulfide or methane as their energy source and carbon dioxide as their carbon source to produce organic molecules. These producers do not rely on sunlight, and instead get their energy from the hydrothermal vents, which contain chemicals that are released from the Earth's interior.

Question 13

What is the % salinity of the ocean?

Accepted Answer

The average salinity of the ocean is around 3.5%, which means that for every 1 liter of seawater, there are about 35 grams of dissolved salts. Option A, C, D and E are not accurate.

Question 14

Which of these regulates the formation of biofilms?

Accepted Answer

Quorum sensing is the signal transduction pathway that bacteria use to communicate with each other and regulate their behavior, such as the formation of biofilms.

Question 15

Which of these is the LEAST important physiological activity to consider when studying an ecosystem?

Accepted Answer

Methane production by methanogens, while important in certain contexts (such as in anaerobic environments and contributing to greenhouse gas emissions), is generally considered less universally crucial to the functioning of ecosystems compared to the other processes listed. Processes like primary production (both chemolithotrophic and phototrophic), decomposition, and biogeochemical cycling are fundamental to the energy flow and nutrient cycling in virtually all ecosystems.

Question 16

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

Accepted Answer

The answer of The coastal marine waters contain on average...

Question 17

FISH is a fluorescent microscopic technique used to differentiate microbes using this fluorescently labeled material.

Accepted Answer

FISH (Fluorescence in situ hybridization) is a technique where fluorescently labeled DNA probes are used to bind to specific sequences of microbial DNA. This allows for differentiation and visualization of specific microbes.

Question 18

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

Accepted Answer

Water availability is not an advantage of living in a biofilm community as water is already present in the environment. The other options, such as protection from predation, toxins, and nutrient availability, as well as genetic exchange, are advantages that can be found in a biofilm community.

Question 19

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

Accepted Answer

Viruses are the most abundant biological entities in the ocean, outnumbering all other groups.

Question 20

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.

Accepted Answer

Operational taxonomic units (OTUs) are defined as groups of microorganisms that share at least 97% sequence identity of their SSU (small subunit) rRNA gene. This is a commonly accepted threshold for defining bacterial and archaeal species based on sequence similarity. OTUs are often used in microbial ecology studies to assess diversity and compare community composition across different samples or environments.

Quiz 15: Microbial Ecosystems