Introduction to Microbiology and Microscopy

Module 1: Introduction to Microbiology

• Microbiology Definition: The study of the biology of microscopic organisms.
• Scope of Study: Includes infection prevention, sterilization, wound cleaning, sample collection, and testing.
• Real-World Applications: Food production, biodegradation, manufacturing processes, genetic engineering.
• Spontaneous Generation Disproval & Germ Theory: Scientists like Pasteur and Koch conducted crucial experiments, methods helping understand microorganisms and disease causation.

Module 2: Microscopy and Staining Techniques

• Units of Measurement:
  • Micrometer (µm): One-millionth of a meter (10⁻⁶ m), used for cells and bacteria.
  • Nanometer (nm): One-billionth of a meter (10⁻⁹ m), used for molecules and viruses.
• Microscope Development:
  • Hooke: First to observe cells, coining the term "cell."
  • Leeuwenhoek: Improved microscope, observed single-celled organisms ("animalcules").
• Microscopy Principles:
  • Total Magnification: Product of objective and ocular lens magnifications (e.g., 10x ocular, 40x objective = 400x).
  • Resolving Power (Resolution): Ability to distinguish close objects as separate.
  • Refraction: Light bending as it passes through different mediums.
  • Contrast: Difference in light intensity between specimen and background (enhanced by staining).
• Brightfield Microscope Parts:
  • Ocular Lens (Eyepiece): Magnifies image (usually 10x).
  • Objective Lenses: Provide further magnification (e.g., 4x, 10x, 40x, 100x).
  • Stage: Holds slide.
  • Light Source: Illuminates specimen.
  • Condenser: Focuses light onto the specimen.
  • Diaphragm: Controls light intensity.
  • Focus Knobs (Coarse & Fine): Adjust image focus.
• Light Pathway: Light source → condenser → diaphragm → specimen → objective lens → ocular lens → eye.
• Microbial Smear Preparation:
  • Place water drop on slide.
  • Transfer microorganism to water drop.
  • Spread evenly.
  • Air dry.
  • Heat fix (pass through flame) for killing and attachment.
• Staining Techniques:
  • Simple Staining: Single dye (e.g., methylene blue).
  • Negative Staining: Stains background, not cells (e.g., nigrosin).
  • Differential Staining: Multiple dyes to distinguish cell types (e.g., Gram staining).
• Gram Staining Steps: Crystal violet → iodine → decolorizer → safranin.

Module 3: Prokaryotic Cell Structure and Function

• Prokaryotic Cell Parts: Cell wall, plasma membrane, cytoplasm, ribosomes, nucleoid, flagella, pili.

• Functions of Cell Parts: (See Module 3 details)

• Human vs. Bacterial Cells: Human cells are eukaryotic (nucleus), bacterial cells are prokaryotic (lack nucleus), and vastly different in size.

• Bacterial Shapes and Arrangements: Cocci (spherical), bacilli (rod-shaped), spirilla (spiral-shaped); various arrangements.

• Flagella vs. Axial Filaments: Both for movement; flagella are long, whip-like, axial filaments are internal in spirochetes.

• Dental Plaque: Sticky film of bacteria, food, and saliva; bacterial acids erode enamel.

• Cell Wall Composition & Gram Staining: Peptidoglycan; Gram-positive thick peptidoglycan (purple), Gram-negative thin peptidoglycan (pink).

• Plasma Membrane Composition & Function: Phospholipid bilayer, proteins regulating substance passage.

• Membrane Transport:

  • Diffusion: High to low concentration.
  • Facilitated Diffusion: Diffusion aided by proteins.
  • Active Transport: Against concentration gradient, needs energy.

• Tonicity & Bacterial Shape:

  • Hypotonic: Water into cell, swelling.
  • Hypertonic: Water out of cell, shrinking.
  • Isotonic: No net water movement.

• Proton Motive Force: Potential energy stored in proton gradient for driving cellular processes (synthesis, rotation, and transport).