(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.