Question 1

Which microorganism is considered phytoplankton?

Accepted Answer

Cyanobacteria are considered phytoplankton because they are photosynthetic microorganisms found in aquatic environments, capable of producing their own food through photosynthesis, similar to plants.

Question 2

Vast numbers of microorganisms are being genetically characterized without culturing them in the laboratory today through ______.

Accepted Answer

Metagenomic sequencing allows for the genetic characterization of microorganisms directly from environmental samples without the need for culturing them in the laboratory. This technique sequences DNA from a mixture of organisms, providing insights into the microbial diversity and functions present in the environment.

Question 3

Select the statement that explains the usefulness of metagenomic analysis in research today.

Accepted Answer

Metagenomic analysis is a powerful tool in research for evaluating microbial diversity, identifying unculturable microorganisms, and detecting the abundance of microorganisms in various environments.

Question 4

The slowly decaying organic litter from plant and animal tissues that is found in the soil is called ______.

Accepted Answer

Detritus refers to the slowly decaying organic matter from plant and animal tissues found in the soil, contributing to the organic component of soil.

Question 5

Which of the following is true of water-saturated soils?

Accepted Answer

Water-saturated soils are environments where oxygen is limited due to the water filling the pore spaces between soil particles, creating conditions that favor anaerobic organisms, which do not require oxygen for growth.

Question 6

The mutualistic partnership between plant roots and microbes is ______.

Accepted Answer

Mycorrhizae refer to the symbiotic association between plant roots and fungi, where the fungi help the plant absorb nutrients from the soil, and in return, the plant provides the fungi with carbohydrates produced through photosynthesis.

Question 7

You have been diagnosed with neurotoxic poisoning after having ingested an algal toxin, called brevetoxin, produced by Karenia brevis. In which food did you likely consume this?

Accepted Answer

Brevetoxin, produced by the marine dinoflagellate Karenia brevis, commonly accumulates in shellfish such as oysters. This process is known as bioaccumulation, where the toxin becomes concentrated in the tissues of organisms higher up the food chain, leading to shellfish poisoning in humans who consume affected shellfish.

Question 8

The bacterium Thiobacillus secretes sulfuric acid into the environment.

Accepted Answer

Thiobacillus is known as an acidophilic bacterium and can secrete sulfuric acid into the environment through its metabolic processes.

Question 9

The majority of Earth's water is found in ______.

Accepted Answer

The majority of Earth's water, about 97%, is found in the oceans.

Question 10

Plastic marine debris was collected from multiple sites in the ocean and examined with electron microscopy and next-generation sequencing. These techniques revealed microbial communities growing on the plastics. Which of the following statements is correct regarding these communities?

Accepted Answer

Electron microscopy and next-generation sequencing can reveal the presence of microbial communities on plastics, including potential members that synthesize enzymes to degrade hydrocarbons, which are the main components of plastics. This is a mechanism by which microbes can adapt to and exploit various niches, including those created by human-made materials like plastics.

Question 11

Metagenomic analysis involves DNA sequencing of various samples taken from a particular habitat.

Accepted Answer

Metagenomic analysis does involve DNA sequencing of various samples taken from a particular habitat to identify and study the genetic makeup of the community of microorganisms living in that habitat.

Question 12

How are the sulfur cycle and the phosphate cycle interconnected?

Accepted Answer

Phosphate is released from rock and soil by sulfuric acid, which is part of the sulfur cycle. This process helps to make phosphate available in the soil for plants, thus connecting the sulfur and phosphate cycles.

Question 13

Which of the following statements concerning metagenomic sequencing is incorrect?

Accepted Answer

Metagenomic sequencing involves the analysis of genetic material recovered directly from environmental samples. It typically does not involve the extraction and fragmentation of proteins as described in option D. Instead, it focuses on DNA or RNA to study the genomic content of microbial communities.

Question 14

You have drained a pond on your property to make it deeper. In the process of using a machine to dig, you ?nd that the mud is black and smells terrible. Your prediction is that ______ bacteria predominate in this area of the mud.

Accepted Answer

The presence of black mud that smells terrible is indicative of anaerobic conditions where sulfur-reducing bacteria thrive. These bacteria use sulfur as an electron acceptor, producing hydrogen sulfide gas, which is responsible for the foul smell.

Question 15

The zone of soil around roots of plants is called the ______.

Accepted Answer

The rhizosphere is the zone of soil around the roots of plants where there is intense microbial activity influenced by substances released by root cells.

Question 16

Most of the organic sulfur is located in _______.

Accepted Answer

Most of the organic sulfur in biological systems is found in certain amino acids (such as cysteine and methionine) and, by extension, in the proteins that are made from those amino acids.

Question 17

The total amount of water in the hydrologic cycle has been decreasing over the last million years.

Accepted Answer

There is no scientific evidence to support the claim that the total amount of water in the hydrologic cycle has been decreasing over the last million years. The cycle is a closed system where water evaporates from the Earth's surface, forms clouds, and then falls back to the surface as precipitation, perpetually cycling through the Earth's atmosphere, oceans, and land. While water availability may fluctuate in certain regions due to climate change or human activities, the overall amount of water in the cycle remains relatively constant over time.

Question 18

Which of the following processes is not a part of metagenomic analysis of an environment?

Accepted Answer

Reverse transcription is not a part of metagenomic analysis because metagenomics typically involves the direct analysis of genetic material from environmental samples, focusing on DNA. Reverse transcription is a process used to convert RNA into DNA, which is not a standard step in metagenomic workflows that primarily deal with DNA sequencing.

Question 19

You are preparing a garden and want to provide the best environment for your plants. Which of the following would you add to the potting soil?

Accepted Answer

Mycorrhizae inoculant is beneficial for plants as it forms a symbiotic relationship with the roots, enhancing water and nutrient absorption, thus improving plant growth and health.

Question 20

Mycorrhizae are the mutualistic relationship between fungi and the roots of certain plants.

Accepted Answer

Mycorrhizae is a mutualistic relationship between fungi and the roots of certain plants where the fungi helps the plant absorb nutrients while being provided with carbohydrates in return.

Quiz 24: Microbes and the Environment