Microscopy and Microbiology Quiz

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.