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Prokayotes

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  • How are eubacteria and archea distinct?

    Both are porkaryotes (no Nucleus or membrane-bund organelles) but differ in cell sutrcutres and genetics. Bacteria have peptidoglycan cell walls, while archea do not and instead have unique polymers.

  • How do prokaryotes adhere to each other or to their substrate?

    Use fimbriae (short, hair-like strucutres) to attached to surfaces an dother cells. Some use capsues, which are sticky outer layers that enhance attachment an protection.

  • Differences in cell walls and membranes of Gram positive and Gram negative bacteria. What is the basis for the Gram stain technique?

    • Gram-positive bacteria have a thick peptidoglycan wall that retains crystal violet, so they appear purple. Gram-negative bacteria have a thin wall and an outer membrane, so they lose crystal violet and stain pink/red with safranin. Their outer membrane also increases antibiotic resistance.

  • How do prokaryotes move around?

    Many use flagella, which rotate like propellers to move the cell through liquid.

    • Movement is often guided by taxis, especially chemotaxis, allowing cells to move toward nutrients or away from harmful chemicals. Some also glide or move along surfaces.

  •  What are plasmids? How is their DNA organized?

    Plasmids are small circular DNA separate from the main chromosome, often carrying useful genes like antibiotic resistance. The main DNA is a single circular chromosome in the nucleoid. Plasmids replicate independently and can be transferred between cells.

  •  How do prokaryotes reproduce? What are some ways prokaryotes can exchange genes?

    binary fission, where DNA replicates and cell splits into two identical

    • Gene exchange (horizontal gene transfer):

      • Transformation: uptake of free DNA from environment

      • Transduction: DNA transferred by bacteriophages (viruses)

      • Conjugation: direct transfer sex pilus, often involving plasmids

    cells.

  •  What is an endospore, a capsule? How is this related to their pathogenicity?

    • endospore is a tough, dormant structure that protects bacterial DNA in extreme conditions. A capsule is a sticky outer layer that helps bacteria attach and evade the immune system. Both increase pathogenicity by improving survival and making infections harder to eliminate.

  • Define the four major modes of nutrition in prokaryotes.

     Based on energy source + carbon source:

    • Photoautotrophs: light energy + CO₂ (ex: cyanobacteria)

    • Chemoautotrophs: inorganic chemicals + CO₂ (ex: nitrogen-fixing bacteria)

  •  What is nitrogen fixation?

    Conversion of atmospheric N₂ into NH₃ (ammonia), which plants and organisms can use to make proteins and nucleic acids.

    • Performed by certain bacteria (ex: Rhizobium in legume root nodules), playing a key role in the nitrogen cycle and ecosystem productivity.

  • Contrast aerobes vs. anaerobes (obligate, facultative).

    • Obligate aerobes: require O₂ for cellular respiration

    • Obligate anaerobes: poisoned by O₂, use fermentation/anaerobic respiration

      • Facultative anaerobes: can switch between aerobic respiration and anaerobic pathways depending on oxygen availability

  • List and describe the types of archaea found in extreme environments (halophiles, etc.).

    • Halophiles: live in high salt (ex: salt lakes)

    • Thermophiles/extreme thermophiles: live in very hot environments

    • Methanogens: live in anaerobic environments (swamps, animal guts) produce methane as byproduct

      • Many archaea extremophiles, adapted to harsh conditions where most life cannot survive.

  • Explain the importance of the human microbiome.

     The human microbiome consists of beneficial microbes that help with digestion, vitamin production (K, B12), immune system development, and protection against pathogens.

    •  Imbalances (dysbiosis) are linked to diseases such as infections, digestive disorders, and immune issues.

  • What is symbiosis?

    What categories of symbiotic relationships are there?

     Symbiosis is a close, long-term ecological interaction between species.

    • Mutualism: both benefit

    • Commensalism: one benefits, other unaffected

    • Parasitism: one benefits, host harmed (parasites that cause disease = pathogens)

  • What is antibiotic resistance and how does it originate? Which are the targets of antibiotics in bacterial cells?

    ability of bacteria to survive exposure to antibiotics, arising from mutations or horizontal gene transfer (R plasmids).

    • spreads through natural selection, like antibiotics are overused.

      • Antibiotics target:

        • Cell wall synthesis

        • Cell membrane function

        • DNA/RNA synthesis

        • Protein synthesis (ribosomes)

  • Which groups of bacteria are believed to be related to ancestral mitochondria and chloroplasts?

    • Mitochondria → evolved from aerobic alpha-proteobacteria

    • Chloroplasts → evolved from photosynthetic cyanobacteria

      • This supports the endosymbiotic theory, where ancestral cells engulfed bacteria that became organelles.

  • Name examples of the applications of bacteria for human activities.

    Bacteria are used in:

    • Biotechnology (E. coli for gene cloning)

    • Genetic engineering (Agrobacterium for plants)

    • Pharmaceuticals

    • Bioremediation (cleaning pollutants like oil spills)

    • Biofuels (ethanol production)

    • Bioplastics (biodegradable materials)

    CRISPR (gene editing technology )