MCB2010 Exam 1 Study Guide: Foundations of Microbiology

Chapter 1: A Brief History of Microbiology

Groups of Microorganisms

• Bacteria: Single-celled prokaryotes with peptidoglycan cell walls.

• Archaea: Prokaryotes without peptidoglycan, often found in extreme environments.

• Fungi: Eukaryotic organisms including yeasts (unicellular) and molds (multicellular).

• Protozoa: Unicellular eukaryotes, often motile.

• Algae: Photosynthetic eukaryotes, can be unicellular or multicellular.

• Viruses: Acellular entities composed of genetic material and a protein coat.

Prokaryotes vs. Eukaryotes

• Prokaryotes: Lack a nucleus and membrane-bound organelles (e.g., Bacteria, Archaea).

• Eukaryotes: Have a nucleus and membrane-bound organelles (e.g., Fungi, Protozoa, Algae).

The Golden Age of Microbiology: Key Questions

• Is spontaneous generation of microbial life possible?

• What causes fermentation?

• What causes disease?

• How can we prevent infection and disease?

Spontaneous Generation

• Supporters: Aristotle, Needham.

• Opponents: Redi, Spallanzani, Pasteur.

• Key Experiments: Redi’s meat and maggots, Needham’s broth, Spallanzani’s sealed flasks, Pasteur’s swan-neck flask.

Major Scientists and Contributions

• Louis Pasteur: Disproved spontaneous generation, developed pasteurization.

• Robert Koch: Identified causative agents of disease, developed Koch’s postulates.

• Joseph Lister: Introduced antiseptic surgery.

• Edward Jenner: Developed smallpox vaccine.

• Florence Nightingale: Advanced hospital sanitation.

Koch’s Postulates

1. The suspected pathogen must be present in all cases of the disease and absent from healthy organisms.

2. The pathogen must be isolated and grown in pure culture.

3. The cultured pathogen must cause disease when introduced into a healthy host.

4. The same pathogen must be re-isolated from the diseased experimental host.

Chapter 2: The Chemistry of Microbiology

Basic Chemical Concepts

• Matter: Anything that occupies space and has mass.

• Atom: The smallest unit of an element, composed of protons, neutrons, and electrons.

• Element: Substance consisting of one type of atom.

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons.

Atomic Structure

• Nucleus: Contains protons (+) and neutrons (0).

• Electrons: Negatively charged, orbit the nucleus in shells.

• Electron Shells: First shell holds 2 electrons, second and third hold up to 8 each.

• Valence Electrons: Electrons in the outermost shell, involved in chemical bonding.

Chemical Bonds

• Nonpolar Covalent Bonds: Electrons shared equally.

• Polar Covalent Bonds: Electrons shared unequally, creating partial charges.

• Ionic Bonds: Transfer of electrons from one atom to another, forming cations (+) and anions (−).

• Hydrogen Bonds: Weak attractions between polar molecules, important in DNA and protein structure.

Chemical Reactions

• Synthesis (Anabolism): Building larger molecules from smaller ones.

• Decomposition (Catabolism): Breaking down molecules into smaller units.

• Exchange: Atoms are exchanged between molecules.

Endothermic vs. Exothermic Reactions

• Endothermic: Absorb energy.

• Exothermic: Release energy.

Water: Properties and Importance

• Excellent solvent

• High heat capacity

• Cohesion and adhesion

• Participates in chemical reactions

• Remains liquid across a wide temperature range

Acids, Bases, Salts, and Buffers

• Acids: Release H+ ions in solution.

• Bases: Accept H+ ions or release OH−.

• Salts: Compounds formed from acid-base reactions.

• Buffers: Stabilize pH by absorbing or releasing H+.

Organic Molecules

• Functional Groups: Specific groups of atoms that confer properties (e.g., hydroxyl, carboxyl).

• Carbohydrates: Composed of C, H, O; provide energy and structure.

• Lipids: Include fats (triglycerides), phospholipids, waxes, steroids.

• Proteins: Made of amino acids; functions include catalysis, structure, transport, regulation, and defense.

• Nucleic Acids: DNA and RNA; store and transfer genetic information.

Structure of Biomolecules

• Fat (Triglyceride): Glycerol + 3 fatty acids.

• Phospholipid: Glycerol + 2 fatty acids + phosphate group.

• Saturated Fatty Acids: No double bonds; solid at room temperature.

• Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

• Amino Acid: Central carbon, amino group, carboxyl group, R group, hydrogen.

• Protein Structure: Primary (sequence), secondary (alpha helix/beta sheet), tertiary (3D folding), quaternary (multiple polypeptides).

• Nucleotide: Sugar, phosphate, nitrogenous base.

• DNA vs. RNA: DNA is double-stranded, deoxyribose sugar; RNA is single-stranded, ribose sugar.

Chapter 3: Cell Structure and Function

Major Processes of Living Cells

• Growth

• Reproduction

• Responsiveness

• Metabolism

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, smaller, simpler structure.

• Eukaryotes: Nucleus, larger, complex organelles.

Glycocalyces: Capsules vs. Slime Layers

• Capsule: Organized, firmly attached to cell wall; protects against phagocytosis.

• Slime Layer: Loose, water-soluble; aids in attachment.

Bacterial Flagella

• Structure: Filament, hook, basal body.

• Function: Motility.

• Arrangements: Monotrichous (single), lophotrichous (tuft), amphitrichous (both ends), peritrichous (all over).

Bacterial Shapes and Arrangements

• Shapes: Coccus (spherical), bacillus (rod), spirillum (spiral), vibrio (comma-shaped), spirochete (flexible spiral).

• Arrangements: Chains (strepto-), clusters (staphylo-), pairs (diplo-).

Peptidoglycan Structure

• Sugar Portion: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

• Peptide Portion: Short chains of amino acids cross-linking the sugars.

Gram-Positive vs. Gram-Negative Cell Walls

• Gram-Positive: Thick peptidoglycan, teichoic acids, stains purple.

• Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharide (LPS), stains pink.

Phospholipid Bilayer and Fluid Mosaic Model

• Phospholipid Bilayer: Hydrophilic heads, hydrophobic tails; forms the cytoplasmic membrane.

• Fluid Mosaic Model: Membrane is flexible with proteins embedded or associated with the bilayer.

Membrane Transport

• Passive Processes: Diffusion, facilitated diffusion, osmosis (no energy required).

• Active Processes: Require energy (ATP); e.g., active transport, group translocation.

Osmosis and Tonicity

• Osmosis: Diffusion of water across a semipermeable membrane.

• Isotonic: Equal solute concentration.

• Hypertonic: Higher solute outside; cell shrinks.

• Hypotonic: Lower solute outside; cell swells.

Bacterial Cytoplasm

• Contains cytosol, inclusions, ribosomes, and sometimes endospores.

• Inclusions: Reserve deposits (e.g., polyhydroxybutyrate, sulfur granules).

Endospores

• Highly resistant, dormant structures formed by some bacteria (e.g., Bacillus, Clostridium).

• Enable survival in harsh conditions.

Ribosomes and Cytoskeleton

• Ribosomes: Sites of protein synthesis; prokaryotic (70S), eukaryotic (80S).

• Cytoskeleton: Protein fibers for shape and support.

Endosymbiotic Theory

• Mitochondria and chloroplasts originated from engulfed prokaryotes.

• Evidence: Double membranes, own DNA, ribosomes similar to bacteria.

Chapter 4: Microscopy, Staining, and Classification

Metric Units in Microbiology

• Primary Units: Micrometer (µm), nanometer (nm).

• Order of Units: Meter (m) > millimeter (mm) > micrometer (µm) > nanometer (nm).

Types of Microscopy

• Bright-Field: Light passes through specimen; best for stained samples.

• Dark-Field: Light reflected off specimen; enhances contrast in unstained samples.

• Phase Microscopy: Enhances contrast using differences in refractive index; good for live cells.

• Transmission Electron Microscope (TEM): Electrons pass through specimen; high resolution, internal structures.

• Scanning Electron Microscope (SEM): Electrons scan surface; 3D images of surfaces.

Staining Techniques

• Simple Stains: Use one dye to highlight cells.

• Differential Stains: Gram stain, acid-fast stain, endospore stain, capsule stain.

• Special Stains: Flagella stain, negative stain.

Taxonomy and Classification

• Purpose: Organize, identify, and name organisms.

• Hierarchy: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

• Binomial Nomenclature: Two-part scientific name (Genus species).

• Linnaean System Modifications: Addition of domains, molecular techniques.

• Three Domains (Woese and Fox): Bacteria, Archaea, Eukarya.

Identification and Classification Procedures

• Physical characteristics

• Biochemical tests

• Serological tests

• Phage typing

• Analysis of nucleic acids