Chapter 22: Prokaryotes: Bacteria and Archaea Flashcards
What are the three common shapes of prokaryotic cells? Provide examples.
Cocci (spherical, e.g., Staphylococcus).
Bacilli (rod-shaped, e.g., Escherichia coli).
Spirilla (spiral-shaped, e.g., Helicobacter pylori).
How do Gram-positive and Gram-negative bacteria differ structurally?
Gram-positive: Thick peptidoglycan layer, retains crystal violet stain (purple).
Gram-negative: Thin peptidoglycan + outer lipid membrane, stains pink (safranin counterstain).
Compare photoautotrophs, chemoautotrophs, and chemoheterotrophs.
Photoautotrophs: Use light + CO₂ (e.g., cyanobacteria).
Chemoautotrophs: Use inorganic chemicals + CO₂ (e.g., Nitrosomonas in nitrogen cycle).
Chemoheterotrophs: Consume organic molecules (e.g., E. coli).
What is nitrogen fixation, and which prokaryotes perform it?
Process: Converting atmospheric N₂ to NH₃ (ammonia).
Examples: Rhizobium (symbiotic with legumes), Azotobacter (free-living).
Define transformation, transduction, and conjugation.
Transformation: Uptake of free DNA from the environment (e.g., Streptococcus pneumoniae).
Transduction: Gene transfer via bacteriophages (e.g., toxin genes in Corynebacterium diphtheriae).
Conjugation: Direct DNA transfer via pilus (e.g., plasmid transfer in E. coli).
What are endospores, and why are they significant?
Structure: Dormant, resistant cells formed under stress (e.g., Bacillus anthracis).
Significance: Survive extreme heat, radiation, and disinfectants.
How do decomposer prokaryotes impact ecosystems?
Break down organic matter, recycling nutrients (e.g., carbon, nitrogen) into soil/water.
Describe a mutualistic relationship involving prokaryotes.
Example: Gut microbiota synthesizing vitamins (e.g., vitamin K) in humans.
Mechanism: Bacteria benefit from nutrients; host gains metabolic byproducts.
List three bacterial pathogens and their associated diseases.
Mycobacterium tuberculosis → Tuberculosis.
Clostridium botulinum → Botulism.
Vibrio cholerae → Cholera.
How are prokaryotes used in bioremediation?
Degrade pollutants (e.g., Deinococcus radiodurans breaks down radioactive waste).
What distinguishes Archaea from Bacteria?
Cell membranes: Archaea have ether-linked lipids; Bacteria have ester-linked lipids.
Extremophiles: Many Archaea thrive in extreme environments (e.g., Methanogens in anaerobic marshes).
Genetics: Archaeal transcription/translation resemble eukaryotes.
Name two extremophile Archaea and their habitats.
Halobacterium: High-salt environments (e.g., Dead Sea).
Thermococcus: Hydrothermal vents (temps >80°C).
How does horizontal gene transfer contribute to antibiotic resistance?
Plasmids carrying resistance genes (e.g., bla for β-lactamase) spread via conjugation.
Why are biofilms problematic in medical settings?
Resist antibiotics and host immune responses (e.g., Pseudomonas aeruginosa in cystic fibrosis lungs).
How do Cyanobacteria impact aquatic ecosystems?
Form harmful algal blooms (HABs), releasing toxins (e.g., microcystin) that kill aquatic life.
What role do methanogens play in the carbon cycle?
Convert CO₂ and H₂ into methane (CH₄) in anaerobic environments (e.g., wetlands, ruminant guts).
Why can’t Archaea be targeted by most antibiotics?
Antibiotics (e.g., penicillin) target bacterial peptidoglycan, which Archaea lack.
Design an experiment to test antibiotic effectiveness against a biofilm.
Grow biofilm in vitro (e.g., Staphylococcus epidermidis on a catheter surface).
Treat with antibiotics at varying concentrations.
Use confocal microscopy to assess biofilm viability (live/dead staining).
