microscopy - chapter 4

CELL STRUCTURES

  • Characteristics of Bacteria

    • Bacteria are unicellular organisms with diverse shapes and arrangements.

    • They possess cell walls, cytoplasmic membranes, and various organelles depending on type.

SPONTANEOUS GENERATION & BIOGENESIS

  • Spontaneous Generation

    • Definition: Belief that life arises from non-living matter.

    • Discredited by Francesco Redi in 1668 through his experiment with rotting meat and flies.

    • Louis Pasteur further disproved this theory, proving contamination from air contains microorganisms.

  • Biogenesis

    • Definition: Life arises from pre-existing living matter.

    • Established as the principle guiding microbiology.

    • Louis Pasteur is known as the father of microbiology due to his contributions.

GERM THEORY

  • Louis Pasteur and Germ Theory

    • Conducted significant experiments linking specific microorganisms to diseases.

    • Suggested boric acid to kill microorganisms in clinical settings.

    • Germ Theory indicates that many diseases are caused by specific microbes.

  • Joseph Lister

    • Known as the "Father of Antiseptic Surgery" for promoting antiseptic techniques.

    • Introduced carbolic acid to sterilize surgical instruments, significantly reducing surgical deaths.

CELL THEORY

  • Robert Hooke

    • Examined cork and discovered cells, coining the term "cells" to describe the compartmental structure.

    • Cell Theory states:

      1. All living things are composed of cells.

      2. The cell is the basic unit of life.

      3. All cells arise from pre-existing cells.

MICROSCOPY

  • Types of Microscopes

    • Basic microscopes first observed microorganisms; modern compound microscopes utilize multiple lenses for magnification.

STAINING TECHNIQUES

  • Wet Mounts

    • Utilized for observing living organisms' motility.

    • Example: Trichomonas.

  • Simple Stains

    • Uses basic dyes to stain cellular components (e.g., methylene blue, crystal violet).

  • Differential Stains

    • Gram Stain

      • Divides bacteria into gram-positive and gram-negative based on cell wall structure.

      • Improper decolorization can affect results.

    • Acid-Fast Stain

      • Identifies bacteria with high waxy content in cell walls, such as Mycobacterium.

      • Uses carbol fuchsin and methylene blue for staining structure.

SPECIAL STAINS

  • Capsule Stain

    • Highlights gelatinous layers around microbes that contribute to virulence.

  • Endospore Stain

    • Stains resistant endospores found in genera like Bacillus and Clostridium.

  • Flagella Stain

    • Visualizes flagella, thin appendages aiding in bacterial motility.

FLUORESCENT DYES & IMMUNOFLUORESCENCE

  • Used to label cellular components and count microbial cells.

  • Distinguishes living and dead cells by binding cellular structures.

  • Immunofluorescence utilizes tagged antibodies for specific protein detection.

BACTERIAL MORPHOLOGY

  • Shapes and Arrangements

    • Bacteria may be spherical (cocci), rod-shaped (bacilli), or spiral. Their arrangements can suggest specific bacterial types.

    • Examples:

      • Diplococci: Pairs (e.g., Streptococcus pneumoniae).

      • Bacilli: Chains (e.g., Bacillus anthracis).

      • Spirals: Various forms (e.g., Helicobacter pylori).

PROKARYOTIC CELL STRUCTURE

  • Importance of Structure

    • Structure is crucial for antibiotic targeting.

  • Cytoplasmic Membrane

    • Acts as a gatekeeper for cellular material.

  • Cell Envelope

    • Composed of cell wall, cytoplasmic membrane, and capsule (if present).

  • Cytoplasm

    • Contains ribosomes, nutrients, and a nucleoid region housing the chromosome.