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(470) Microbiology lecture 1 | Bacteria structure and function

Introduction to Microbiology

  • Overview of the microbiology lecture series, focusing on bacterial structure and function.

  • Discussion includes components like the cell wall, fimbriae, and pili.

Characteristics of Living Cells

  • Living organisms consist of cells, which can be single (unicellular) or multiple (multicellular).

  • Basic cell shapes: spherical, cubical, cylindrical.

  • Cells contain cytoplasm encased by a membrane.

Eukaryotic vs. Prokaryotic Cells

  • Eukaryotic Cells: Organized with membrane-bound organelles (e.g., mitochondria, Golgi bodies).

    • Contain a nucleus with genetic material (DNA).

    • Examples: Animals, plants, fungi, protists.

  • Prokaryotic Cells: Simpler, without membrane-bound organelles and no nucleus.

    • Genetic material is free-floating in the cytosol.

    • Examples: Bacteria, Archaea.

Prokaryotic Cell Structure

  • Diagram illustrating prokaryotic cell structure, showcasing genetic material and cell membrane.

  • Prokaryotic cells lack compartmentalization found in eukaryotic cells.

Characteristics of Life

  • Reproduction (sexual or asexual) is vital for continuity.

  • Growth and development, metabolism, and movement (motility) are critical functions.

  • Motility: Driven by internal or external signaling, aiding in finding food and survival.

  • Mechanisms for storage and protection, including cell walls and vacuoles, are essential.

Structural Overview of Bacterial Cells

  • Bacterial cells contain DNA, ribosomes, cytoplasm, and protective membranes.

  • Cytoskeletal Elements: Maintain cell shape and connect internal components.

Cytoplasmic Extensions

  • Fimbriae and Pili: Hair-like structures aiding in adhesion and motility.

    • Flagella: Complex structure aiding in motility, composed of flagellin.

    • Mixtures of Extensions: Assist in adherence to host cells.

    • Glycocalyx: Protective layer made of carbohydrates, unrestricted outside the cell wall.

Appendages and Glycocalyx

  • Function of external structures classified into appendages (fimbriae, pili, flagella) and glycocalyx.

  • Role of glycocalyx in protection against host defenses and aiding adherence to surfaces.

  • Biofilms: Communities of bacteria adhered to surfaces, difficult to eliminate due to their protective coating.

Flagella Structure

  • Flagella composed of filament, hook, and basal body.

    • Chemotaxis: Movement towards chemical gradients, impacting bacterial behavior.

    • Types of flagellar arrangements: monotrichous, lophotrichous, amphitrichous, peritrichous.

    • Variation in movement style depending on flagellar arrangement.

Cell Envelope Structure

  • Comprised of two layers: cell wall and cell membrane.

  • Two types of bacteria shown in Gram stain: Gram-positive (thick peptidoglycan wall) and Gram-negative (thin peptidoglycan with additional membrane).

Bacterial Cell Membrane

  • Phospholipid bilayer with proteins: involved in energy reactions, nutrient processing, and selective permeability.

Internal Cell Components

  • Cytoplasm: Mostly water with dissolved molecules; site for metabolic activities.

  • Genetic Material: Nucleoid contains a circular double-stranded DNA chromosome. Plasmids provide additional genetic traits (e.g., antibiotic resistance).

  • Ribosomes: Smaller than eukaryotic (70S vs. 80S), crucial for protein synthesis.

  • Inclusions and Granules: Storage bodies for nutrients, rare compared to plant vacuoles.

  • Cytoskeleton: Provides structure and shape to the cell.

Conclusion

  • Overview of bacterial structure and functions discussed extensively.

  • Acknowledgment of the importance of understanding bacterial characteristics in microbiology.