Microscopy and Microbiology Quiz

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Questions and Answers

What is the purpose of phase contrast microscopy?

To visualize specimens at the atomic level

To visualize dense specimens without the need for staining

To visualize specimens in 3D

To visualize transparent specimens without the need for staining (correct)

What is the main difference between gram-positive and gram-negative bacteria?

Presence of a thick peptidoglycan layer in gram-positive and a thin layer in gram-negative (correct)

Presence of a nucleus in gram-positive and an absence of a nucleus in gram-negative

Presence of a thin peptidoglycan layer in gram-positive and a thick layer in gram-negative

Presence of a cell wall in gram-positive and an absence of a cell wall in gram-negative

What is the function of chloroplasts in eukaryotic microbes?

Cellular respiration

Photosynthesis (correct)

DNA replication

Protein synthesis

What is the purpose of differential media in bacterial culture?

To distinguish between different types of bacteria based on their growth characteristics Signup and view all the answers

What are the two culture-independent methods to study microbial communities?

16/18s rRNA amplicon sequencing and metagenomics Signup and view all the answers

Which microbial groups have metabolic strategies based on energy and carbon sources?

Green sulfur bacteria, iron oxidizing bacteria, heterotrophic bacteria, and cyanobacteria Signup and view all the answers

What are the mechanisms of horizontal gene transfer?

Transduction, transformation, conjugation Signup and view all the answers

In which industrial applications are microbes commonly involved?

Fermentation in bread and kombucha production, algal biofuels, bioremediation, & phage therapy Signup and view all the answers

Which of the following correctly describes symbiogenesis theory?

It proposes that eukaryotic organelles, such as mitochondria and chloroplasts, originated from free-living prokaryotes through endosymbiosis. Signup and view all the answers

What distinguishes acid-fast bacteria from Gram-positive and Gram-negative bacteria?

They resist decolorization by acid-alcohol after staining with basic fuchsin. Signup and view all the answers

What is the significance of the 'Great Plate Count Anomaly' in microbiology?

It challenges the accuracy of plate count methods in quantifying viable bacteria in certain environments. Signup and view all the answers

What distinguishes the metabolic strategies of green sulfur bacteria from cyanobacteria?

Utilization of light as an energy source Signup and view all the answers

What distinguishes bacteriostatic antibiotics from bactericidal antibiotics?

Bacteriostatic antibiotics inhibit the growth and reproduction of bacteria, while bactericidal antibiotics directly kill bacterial cells. Signup and view all the answers

In lytic virus replication, what is the function of the protein coat of the virus?

It protects the viral genetic material Signup and view all the answers

What is the role of conjugation in horizontal gene transfer among bacteria?

Direct transfer of DNA through a pilus Signup and view all the answers

What characteristic distinguishes halophiles from thermophiles and psychrophiles?

Prefer high salt environments Signup and view all the answers

Study Notes

Phase Contrast Microscopy

Enhances contrast in transparent samples, enabling detailed observation of live cells without staining.
Particularly useful for viewing cellular structures such as organelles and other subcellular components.

Gram-Positive vs. Gram-Negative Bacteria

Gram-positive bacteria possess a thick peptidoglycan layer and retain the purple crystal violet stain during Gram staining.
Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane; they stain pink due to the safranin counterstain.

Function of Chloroplasts in Eukaryotic Microbes

Chloroplasts are responsible for photosynthesis, converting light energy into chemical energy (glucose) using sunlight, carbon dioxide, and water.
They contain chlorophyll, which captures light energy.

Purpose of Differential Media in Bacterial Culture

Differential media allows differentiation of bacterial species based on specific biochemical characteristics, such as color changes indicating metabolic activity.
Enables identification of bacteria through their growth patterns and reactions on the medium.

Culture-Independent Methods to Study Microbial Communities

Metagenomics analyzes genetic material recovered directly from environmental samples to study microbial diversity and function.
Metatranscriptomics focuses on the collective mRNA transcripts of microbial consortia, revealing active metabolic pathways.

Microbial Groups with Metabolic Strategies

Microbial groups are classified based on how they obtain energy (chemoheterotrophs, photoautotrophs) and carbon sources (organic vs. inorganic).
For example, phototrophic bacteria utilize light energy, while chemolithotrophic bacteria derive energy from inorganic compounds.

Mechanisms of Horizontal Gene Transfer

Horizontal gene transfer occurs through transformation (uptake of naked DNA), transduction (bacteriophage-mediated transfer), and conjugation (direct transfer between bacteria).
These mechanisms contribute to genetic diversity and antibiotic resistance in bacterial populations.

Industrial Applications of Microbes

Microbes are used in fermentation processes to produce alcohol, yogurt, and vinegar.
They are also employed in biotechnology for the production of enzymes, biofuels, and pharmaceuticals.

Symbiogenesis Theory

Symbiogenesis theory proposes that new species arise through the merging of different organisms into a single entity, leading to increased complexity and new traits.
This concept highlights the importance of symbiotic relationships in evolution.

Distinction of Acid-Fast Bacteria

Acid-fast bacteria, like Mycobacterium species, have a waxy cell wall that retains stain despite acid-alcohol treatment, distinguishing them from Gram-positive and Gram-negative bacteria.
This characteristic is crucial for identifying pathogens causing diseases such as tuberculosis.

Significance of the Great Plate Count Anomaly

The Great Plate Count Anomaly refers to the observation that only a small fraction of microbial species can be cultured in laboratory conditions, despite being abundant in natural environments.
Highlights the gap between cultured and uncultured microbial diversity.

Metabolic Strategies of Green Sulfur Bacteria vs. Cyanobacteria

Green sulfur bacteria use light for energy but rely on inorganic compounds (e.g., hydrogen sulfide) for carbon and cannot perform oxygenic photosynthesis.
Cyanobacteria perform oxygenic photosynthesis, producing oxygen as a byproduct while using water and light energy.

Bacteriostatic vs. Bactericidal Antibiotics

Bacteriostatic antibiotics inhibit bacterial growth and reproduction without killing the bacteria, requiring the immune system to eliminate the infection.
Bactericidal antibiotics kill bacteria directly, offering a more definitive treatment for infections.

Function of Protein Coat in Lytic Virus Replication

The protein coat (capsid) protects the viral genetic material and facilitates attachment and entry into host cells.
It is essential for the infectivity and stability of the virus in the external environment.

Role of Conjugation in Horizontal Gene Transfer

Conjugation involves the direct transfer of DNA from one bacterium to another through physical contact, often mediated by a pilus.
This process allows for the exchange of plasmids and can spread antibiotic resistance among bacterial populations.

Distinguishing Characteristics of Halophiles, Thermophiles, and Psychrophiles

Halophiles thrive in high-salt environments, while thermophiles prefer hot conditions, typically above 45°C.
Psychrophiles are adapted to cold environments, with optimal growth at temperatures below 15°C.

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Description

Test your knowledge on microscopy techniques such as bright field, phase contrast, reflected light/inverted microscopes, confocal microscopes and electron microscopes. Also, explore the structure and function of various microorganisms including prions, viruses, viroids, bacteria, archaea, and eukaryotic microbes.