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Questions and Answers

Which of the following is NOT a reason microbes can be difficult to classify?

As asexual organisms, the species concept does not apply to them.

They can exchange genes in non-sexual ways.

Their DNA is easily acquired, amplified, and compared using modern techniques. (correct)

They are difficult to distinguish using microscopy or culture.

Which one of the following is NOT one of Koch's postulates?

When the microbe is introduced into a healthy, susceptible host, the same disease occurs.

The microbe is isolated from the diseased host and grown in pure culture.

The microbe becomes more virulent with each successive host. (correct)

The microbe is found in all cases of disease, but is absent in healthy individuals.

Though there are some exceptions and contradictions to the definition, which of the below best fits the definition of a microbe?

Any virus

Any disease-causing organism

Any bacteria

Any organisms that require a microscope to be seen (correct)

The collection of sequences sampled from a particular environmental sample is called:

Metagenome Signup and view all the answers

A pure culture refers to:

A culture that contains a single type or strain of microorganism. Signup and view all the answers

Which of the following is true of viruses?

They are not cells. Signup and view all the answers

Which of the following organisms are not considered microbes?

Mosquitoes Signup and view all the answers

Pure cultures:

Are isolated microbial species taken from samples that often contain multiple species. Signup and view all the answers

Koch's postulates are criteria used to establish that:

A particular microbe causes a particular disease. Signup and view all the answers

Which of the following is a unique characteristic of viruses that distinguishes them from the other major groups of microorganisms?

Lack of cell structure Signup and view all the answers

The reduction of N2 gas into ammonia is known as:

Nitrogen fixation Signup and view all the answers

Which scientist contributed to disproving spontaneous generation?

John Tyndall Signup and view all the answers

Substances that are naturally produced by microorganisms and that can inhibit or destroy other microorganisms are called _____

antibiotics Signup and view all the answers

Regarding the classification of microbes, which of the following among A-C is false?

A, B, and C are all true. Signup and view all the answers

The first person to visualize a microbe was:

Antoine van Leeuwenhoek Signup and view all the answers

The 'rock-eating' bacteria are typically known as:

Lithotrophs Signup and view all the answers

How did early microbial ecologists determine that microbes are responsible for ecological reactions?

By applying heat and antimicrobial treatment to sewage samples and observing that nitrate was no longer formed. Signup and view all the answers

Penicillin is:

Produced by a mold and was discovered accidentally. Signup and view all the answers

Archaea are prokaryotic cells, yet based on the comparative analysis of _____ archaea are more closely related to eukaryotes than to bacteria.

ribosomal RNA Signup and view all the answers

Dr. Rita Colwell originated the concept of 'viable but nonculturable' microorganisms. Which of the following best describes this concept?

Microorganisms that are alive but are in a state of low metabolic activity and cannot be cultured in a laboratory. Signup and view all the answers

Based on the following DNA sequence comparisons, which two unidentified microorganisms would you conclude are most closely related?

Both microbial genomes include a gene that encodes for streptokinase, an enzyme and virulence factor that activates human plasminogen. Signup and view all the answers

Identify which organisms can be infected by viruses.

Animals Signup and view all the answers

Louis Pasteur and his swan-necked flask. This apparatus was used to show that:

Oxygen does not allow spontaneous generation. Signup and view all the answers

The theory that organisms can arise from inanimate matter is called:

Spontaneous generation Signup and view all the answers

Archaeans:

Are prokaryotic like bacteria, but their gene expression machinery is more similar to eukaryotic organisms. Signup and view all the answers

Most organisms (including you) break down organic compounds to obtain energy and nutritional building blocks. In contrast, chemolithotrophs are prokaryotes that obtain energy through the oxidation of inorganic compounds. Which of the following inorganic molecules would these microbes also need to build macromolecules for new cell material?

CO2 Signup and view all the answers

The use of microbial metabolism to remove or neutralize human waste and industrial pollutants is known as _____

bioremediation Signup and view all the answers

Identify which two of Koch's postulates would most likely not be fulfilled when trying to link a human virus to a particular disease.

When the microbe is introduced into a healthy, nonhuman experimental host, the same disease occurs. Signup and view all the answers

While repeating Pasteur's experiment with the swan-necked flask, John Tyndall occasionally observed the opposite result. Tyndall noticed that the boiled broth in the swan-necked flask sometimes did give rise to microorganisms. Accordingly, he demonstrated that the broth was contaminated with _____

endospores Signup and view all the answers

Which characteristic of endospores led to confusion when Tyndall tried to replicate Pasteur's experiments regarding spontaneous generation?

Heat resistance Signup and view all the answers

Antibiotics are:

Sometimes overprescribed. Signup and view all the answers

During a period of time outside the host, a virus may become _____ and lose many factors that are required for infections. These viruses stimulate the immune system with much lower mortality than the fully virulent strains.

attenuated Signup and view all the answers

The figure below shows a Winogradsky column. High levels of oxygen are available on the upper layers and can be used as an electron acceptor. Which organisms would you expect to use other electron acceptors?

Sulfur-reducing bacteria Signup and view all the answers

Which of the following is a difference between antiseptics and antibiotics?

Antibiotics can be taken internally but antiseptics cannot. Signup and view all the answers

In 1899, Beijerinck found that the infectious agent of tobacco mosaic disease went through a filter of 0.1μm pore size. Stanley later purified and crystallized the infectious agent from infected tobacco leaves. The infectious agent was found to be a(n):

Virus Signup and view all the answers

Sergei Winogradsky:

Discovered chemolithotrophs in natural environments. Signup and view all the answers

Early microscopes:

Showed cells in living material. Signup and view all the answers

Which of the following would allow a disease-causing microbe NOT to adhere to Koch's postulates?

The microbe is found in all patients with a particular disease but also some patients without symptoms. Signup and view all the answers

Carl Woese proposed the domain classification

To account for two major and distinct prokaryotic groups in addition to eukaryotes. Signup and view all the answers

Study Notes

Classification Challenges of Microbes

Microbes possess DNA that is readily acquired and analyzed but exhibit difficulties in classification.
Asexual reproduction complicates the application of traditional species concepts.
Microbial gene exchange occurs through non-sexual processes, complicating classification.
Distinction of microbes via microscopy or culture poses significant challenges.

Koch's Postulates

Koch's postulates provide a framework to confirm the causative relationship between microbes and diseases.
One postulate states that the microbe must be isolated from the diseased host and reacquired through pure culture.
Another asserts the microbe should be present in diseased hosts but absent in healthy individuals.
The assertion that a microbe becomes more virulent with each host is NOT a postulate.

Definition of Microbes

Microbes are defined as organisms that cannot be seen without a microscope, including bacteria, viruses, fungi, and protozoa.

Metagenome

Metagenomes refer to the collective sequences derived from an environmental sample, highlighting microbial diversity.

Pure Culture Definition

A pure culture consists of a single type or strain of microorganism, critical for studying specific pathogens.

Characteristics of Viruses

Viruses are non-cellular entities, distinguishing them from prokaryotic and eukaryotic organisms.

Non-Microbial Organisms

Mosquitoes are not classified as microbes, whereas viruses, bacteria, fungi, and protozoa are.

Characteristics of Pure Cultures

Pure cultures originate from isolated microbial species, which can arise from mixed samples through specific techniques like serial dilution.

Contributions of Scientists

John Tyndall played a significant role in demonstrating the refutation of spontaneous generation.
Antoine van Leeuwenhoek was the first to visualize microbes under a microscope.

Antibiotics

Antibiotics are natural substances produced by microorganisms that can inhibit or kill other microbes.
They may sometimes be overprescribed, leading to resistance issues.

Nitrogen Fixation

Nitrogen fixation is the biochemical process that converts nitrogen gas (N2) into ammonia.

Bioremediation

The use of microbial metabolism for the removal or neutralization of pollutants is termed bioremediation.

Empirical Observations

Early microbial ecologists determined microbial roles in environmental reactions through experimental contamination studies and pure culture observations.

Endospores and Confusion in Experiments

Tyndall's replication attempts were complicated by the presence of heat-resistant endospores, leading to occasional microbial growth in seemingly sterile conditions.

Differences in Microbial Substances

Antiseptics and antibiotics serve differing roles; antibiotics can be administered internally, while antiseptics are primarily for surface application.

Classification of Microorganisms

The domain classification proposed by Carl Woese includes two distinct prokaryotic groups—Archaea and Bacteria—besides Eukarya.

Viral Infections

Viruses can infect a wide range of organisms: animals, plants, archaea, bacteria, fungi, and protists.

Tyndall's Contributions

Tyndall provided insights into microbial persistence and variation in results due to contaminants in experimental setups.

Pathogen Adherence to Koch's Postulates

Some pathogens, like those causing rabies, can infect multiple species, complicating adherence to Koch's postulates due to variability in infection outcomes.

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Untitled Quiz

Questions and Answers

Which of the following is NOT a reason microbes can be difficult to classify?

Which one of the following is NOT one of Koch's postulates?

Though there are some exceptions and contradictions to the definition, which of the below best fits the definition of a microbe?

The collection of sequences sampled from a particular environmental sample is called:

A pure culture refers to:

Which of the following is true of viruses?

Which of the following organisms are not considered microbes?

Pure cultures:

Koch's postulates are criteria used to establish that:

Which of the following is a unique characteristic of viruses that distinguishes them from the other major groups of microorganisms?

The reduction of N2 gas into ammonia is known as:

Which scientist contributed to disproving spontaneous generation?

Substances that are naturally produced by microorganisms and that can inhibit or destroy other microorganisms are called _____

Regarding the classification of microbes, which of the following among A-C is false?

The first person to visualize a microbe was:

The 'rock-eating' bacteria are typically known as:

How did early microbial ecologists determine that microbes are responsible for ecological reactions?

Penicillin is:

Archaea are prokaryotic cells, yet based on the comparative analysis of _____ archaea are more closely related to eukaryotes than to bacteria.

Dr. Rita Colwell originated the concept of 'viable but nonculturable' microorganisms. Which of the following best describes this concept?

Based on the following DNA sequence comparisons, which two unidentified microorganisms would you conclude are most closely related?

Identify which organisms can be infected by viruses.

Louis Pasteur and his swan-necked flask. This apparatus was used to show that:

The theory that organisms can arise from inanimate matter is called:

Archaeans:

The use of microbial metabolism to remove or neutralize human waste and industrial pollutants is known as _____

Identify which two of Koch's postulates would most likely not be fulfilled when trying to link a human virus to a particular disease.

While repeating Pasteur's experiment with the swan-necked flask, John Tyndall occasionally observed the opposite result. Tyndall noticed that the boiled broth in the swan-necked flask sometimes did give rise to microorganisms. Accordingly, he demonstrated that the broth was contaminated with _____

Which characteristic of endospores led to confusion when Tyndall tried to replicate Pasteur's experiments regarding spontaneous generation?

Antibiotics are:

During a period of time outside the host, a virus may become _____ and lose many factors that are required for infections. These viruses stimulate the immune system with much lower mortality than the fully virulent strains.

The figure below shows a Winogradsky column. High levels of oxygen are available on the upper layers and can be used as an electron acceptor. Which organisms would you expect to use other electron acceptors?

Which of the following is a difference between antiseptics and antibiotics?

In 1899, Beijerinck found that the infectious agent of tobacco mosaic disease went through a filter of 0.1μm pore size. Stanley later purified and crystallized the infectious agent from infected tobacco leaves. The infectious agent was found to be a(n):

Sergei Winogradsky:

Early microscopes:

Which of the following would allow a disease-causing microbe NOT to adhere to Koch's postulates?

Carl Woese proposed the domain classification

Study Notes

Classification Challenges of Microbes

Koch's Postulates

Definition of Microbes

Metagenome

Pure Culture Definition

Characteristics of Viruses

Non-Microbial Organisms

Characteristics of Pure Cultures

Contributions of Scientists

Antibiotics

Nitrogen Fixation

Bioremediation

Empirical Observations

Endospores and Confusion in Experiments

Differences in Microbial Substances

Classification of Microorganisms

Viral Infections

Tyndall's Contributions

Pathogen Adherence to Koch's Postulates

Studying That Suits You

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