Microbiology Quiz: Bacteria and Archaea

Bacteria and Archaea (Chapter 27)

• Prokaryotes: Single-celled organisms lacking a nucleus and membrane-bound organelles. Bacteria and Archaea are two distinct domains.
• Gram Stain: Differentiates bacteria based on cell wall structure (peptidoglycan). Gram-positive stain purple, Gram-negative stain pink, gram negative bacteria have an outer membrane.
• Motility: Many bacteria use flagella (different structures). Other methods include gliding and twitching.
• Irreducible Complexity: A concept arguing that complex structures like flagella couldn't evolve through gradual changes. Evolutionary biology refutes this, highlighting co-option of pre-existing proteins.
• Genetic Information Gain: Bacteria acquire new genes via horizontal gene transfer (transformation, transduction, conjugation).
• F-Factor: A plasmid enabling bacterial conjugation.
• Nutritional Modes:
  • Autotrophs: Produce their own food (photosynthesis, chemosynthesis).
  • Heterotrophs: Obtain organic molecules from other organisms (decomposers, parasites).
  • Mixotrophs: Switch between autotrophy and heterotrophy.
• Oxygen Roles:
  • Obligate aerobes: Require oxygen.
  • Obligate anaerobes: Oxygen is toxic.
  • Facultative anaerobes: Can survive with or without oxygen.
• Metabolic Cooperation: Prokaryotes cooperate (biofilms, nitrogen-fixing cyanobacteria).
• Bacterial Diversity: Extensive genetic and metabolic variation exists.
• Archaea vs. Bacteria: Key Differences:
  • Cell Wall: Bacteria have peptidoglycan; Archaea do not.
  • Membrane Lipids: Bacteria have unbranched fatty acids; Archaea have branched hydrocarbons.
  • RNA Polymerase: Bacterial RNA polymerase is simpler; Archaeal is more similar to eukaryotes.
  • Environment: Bacteria are found more widely than archaea, and archaea often thrive in extreme environments.
• Proteobacteria (5 Groups): Key groups with diverse roles (Nitrogen-fixing, pathogens such as Salmonella, E. coli, and Helicobacter pylori).
• Additional Bacterial Groups: Chlamydias (intracellular parasites), Spirochetes (spiral shaped bacteria, Lyme disease), Cyanobacteria (photosynthetic, produce oxygen), Gram-positive bacteria (Streptococcus, Staphylococcus).
• Extremophiles (Archaea): Adapted to extreme environments
  • Thermophiles: Thrive in heat.
  • Halophiles: Thrive in high salt.
  • Methanogens: Produce methane.

Protists (Chapter 28)

• Definition: Mostly unicellular eukaryotes, exhibiting vast diversity.
• Four Supergroups: Excavates, SAR, Rhizarians, Unikonts.
• Excavates (Diplomonads & Parabasalids): Lack mitochondria, often anaerobic.
• Excavates (Euglenozoans):
  • Kinetoplastids: Single large mitochondrion, some parasitic.
  • Euglenids: Mixotrophic, have an eyespot.
• SAR Supergroup (Stramenopiles):
  • Diatoms: Glassy silica walls, major producers in oceans.
  • Golden Algae: Photosynthetic, some mixotrophic.
  • Brown Algae: Multicellular, kelp, alternation of generations.
• SAR Supergroup (Alveolates):
  • Dinoflagellates: Cause red tides, some bioluminescent.
  • Apicomplexans: Parasitic (e.g., Plasmodium – malaria).
  • Ciliates: Use cilia for movement and feeding (e.g., Paramecium).
• Rhizarians:
  • Radiolarians: Silica skeletons, use pseudopodia.
  • Forams: Calcium carbonate shells, contributors to marine sediments.
  • Cercozoans: Amoeboid, some photosynthetic.
• Nutrient Acquisition: Diverse feeding strategies (parasitism, mixotrophy, photosynthesis).
• Structural Components: Different structures based on group (silica walls, calcium carbonate shells, cilia, flagella, plant-like structures).

Fungi (Chapter 31)

• Definition: Heterotrophic decomposers that absorb nutrients via extracellular digestion.
• Body Structure: Composed of hyphae forming a mycelium.
• Reproduction:
  • Sexual: Plasmogamy (cytoplasm fusion) followed by karyogamy (nuclear fusion).
  • Asexual: Spore formation.
• Fungal Phyla:
  • Chytrids: Flagellated spores, aquatic.
  • Zygomycetes: Rapidly growing molds.
  • Glomeromycetes: Mycorrhizal symbionts.
  • Ascomycetes: Sac fungi (e.g., yeast, truffles).
  • Basidiomycetes: Club fungi (e.g., mushrooms).
• Ecological Roles:
  • Decomposers: Breakdown organic matter.
  • Mutualists: Mycorrhizae (fungi + plant roots).
  • Pathogens: Cause fungal diseases in plants and animals.