ProkaryotesAndProtists

Prokaryotes

• Definition: Prokaryotes are single-celled organisms that lack a nucleus and membrane-bound organelles. They are characterized by a simple structure compared to eukaryotic cells.

Common Shapes of Bacterial Cells

• Common Shapes:

  • Spherical (Cocci): Round bacteria.

  • Rod-shaped (Bacilli): Cylindrical bacteria.

  • Spiral: Curved or spiral-shaped bacteria.

Overview of Parts of a Bacterial Cell

Typical Bacterial Cell Structure

• Bacterial Wall: Provides structural support and protection.

• Slime Layer or Capsule: A protective layer that aids in avoiding the immune response.

• Cell Wall: Composed of peptidoglycan, it is essential for cell shape.

• Plasma Membrane: A lipid bilayer that regulates what enters and leaves the cell.

• Appendages:

  • Flagella: Used for movement.

  • Pili or Fimbriae: Hair-like structures that aid in attachment to surfaces.

• Protoplasm:

  • Cytoplasm: Gel-like substance where cellular processes occur.

  • Ribosome: Site of protein synthesis.

  • Chromatophore: Involved in photosynthesis in certain bacteria.

  • Vacuole: Storage for nutrients, waste products, etc.

• Nuclear Material:

  • Nucleoid: Region containing the cell’s genetic material (DNA).

  • Plasmid: Small circular DNA that carries additional genes.

  • Episome: A type of plasmid that can integrate into the chromosome.

Parts of a Bacterial Cell

• Components include plasma membrane, cell wall, nucleoid (DNA), ribosomes, capsule, plasmid, pili, flagellum, and cytoplasm.

Cell Wall Structure

• Structure:

  • Peptidoglycan Layer: A glycoprotein layer providing rigidity and shape to the cell, located between the inner and outer membranes.

  • Gram-positive Bacteria: Thick cell wall.

  • Gram-negative Bacteria: Thinner cell wall with an outer membrane.

• Peptidoglycan Synthesis Components: Includes surface proteins, glycoproteins, lipoteichoic acids, and lipopolysaccharides.

Respiratory Membrane - Cell Respiration

• Function: Embedded electron transport chain complexes in the inner cell membrane facilitate respiration in bacteria.

Thylakoid Membrane - Photosynthesis

• Function: Houses electron transport chains for photosynthesis in cyanobacteria.

Capsule

• Definition: A well-organized protective layer covering the outer surface of some bacterial cells.

Endospore Formation

• Definition: A resistant structure formed by some bacteria to withstand adverse environmental conditions.

Fimbriae

• Function: Long, slender protein tubes that help anchor bacterial cells to surfaces, functioning like Velcro.

Flagella

• Definition: A whip-like structure aiding in bacterial mobility, composed of proteins; includes components like a hook and filament.

Pili

• Function: Hollow protein tubes used for connecting bacterial cells for genetic material exchange.

Bacterial Conjugation - Sexual Reproduction

• Stages:

  1. Donor and recipient cells align.

  2. Transfer of chromosomal DNA through pilus.

  3. DNA integration and replication in the recipient.

Binary Fission - Asexual Reproduction

• Process:

  1. Parent cell

  2. DNA duplicates.

  3. Cytoplasm divides leading to two daughter cells.

Bacterial Energy Acquisition

Different Ways Bacteria Obtain Energy

• Chemotrophy: Using chemicals (organic/inorganic) to obtain energy.

• Phototrophy: Using light to obtain energy.

Nutritional Types

• Chemoorganotrophs: Organic chemicals.

• Chemolithotrophs: Inorganic chemicals.

• Phototrophs: Light sources.

Overview of Domains of Life

• Three Domains: Eukarya, Archaea, Bacteria.

• Notable Groups:

  • Eukarya: Contains all eukaryotic organisms.

  • Archaea: Often extremophiles, unique cell wall composition.

  • Bacteria: Vastly diverse group including gram-positive and gram-negative bacteria.

Specific Bacterial Groups

Proteobacteria

• Characteristics: Gram-negative; mitochondria evolved from this group.

• Examples: Thiomargarita namibiensis, Neisseria gonorrhoeae, Vibrio cholerae, Helicobacter pylori.

Chlamydias

• Characteristics: Gram-negative, parasites that exist only in animal cells; lack peptidoglycan.

• Example: Chlamydia trachomatis.

Spirochetes

• Characteristics: Notable for spiral shape; gram-negative.

• Examples: Treponema pallidum, Borrelia burgdorferi.

Cyanobacteria

• Characteristics: Photoautotrophic; believed to be ancestors of chloroplasts.

• Examples: Anabaena, Oscillatoria, Cylindrospermum.

Gram-Positive Bacteria

• Characteristics: Diverse, many cultured for antibiotics.

• Examples: Staphylococcus aureus, Bacillus anthracis, Clostridium botulinum.

Comparison of the Three Domains of Life

Key Characteristics:

• Nuclear Envelope: Absent in Bacteria and Archaea, present in Eukarya.

• Organelles: Bacteria and Archaea lack membrane-bound organelles; Eukarya have them.

• Peptidoglycan in Cell Wall: Present in Bacteria, absent in Archaea and Eukarya.

• Growth at High Temperatures: Some Archaea can grow at temperatures > 100°C.

Chemical Recycling

• Nitrogen Cycle: Bacteria converting atmospheric nitrogen (N2) into ammonia (NH3).

  • Functions:

    • Nitrogen-fixing bacteria convert N2 to NH3.

    • Denitrifying bacteria convert nitrates to N2.

    • Nitrifying bacteria change NH3 into nitrites and nitrates.

• Carbon Cycle: Photosynthetic bacteria fix CO2, decomposers recycle carbon back to the atmosphere.

Symbiosis

• Definition: Close interaction between two or more species.

• Types:

  • Mutualism (+/+): Both species benefit.

  • Commensalism (+/0): One species benefits, the other is unaffected.

  • Parasitism (+/-): One species benefits at the expense of another.

Endosymbiotic Theory

• Concept: Proposes that eukaryotic cells originated through a symbiotic relationship between different species of prokaryotes.

• Key Stages:

  • An ancestral prokaryote engulfs an aerobic prokaryote, becoming a mitochondrion.

  • A cyanobacterium is engulfed, forming a chloroplast.

Secondary Symbiosis and 4 Supergroups

• Examples of Supergroups:

  • Red Algae: Contain specialized pigments.

  • Dinoflagellates: Notable for bioluminescence and causing red tides.

  • Apicomplexans: Parasitic pathogens like Plasmodium.

  • Ciliates: Complex organelles and structures for movement and feeding.

Summary of Major Algal Groups

• Types of Algae:

  • Red Algae: Phycoerythrin pigments.

  • Green Algae: Contain chlorophyll a and b.

  • Brown Algae: Includes kelps and is important in marine environments.

  • Golden Brown Algae: Characteristic color due to fucoxanthin.

Conclusion

• This comprehensive overview emphasizes the diversity and complexity of prokaryotic and eukaryotic life forms, their structural features, reproductive strategies, and ecological roles within their environments.