MCB2010 Exam 1 Study Guide: Microbiology Fundamentals

Chapter 1: A Brief History of Microbiology

Groups of Microorganisms

Microorganisms are diverse and classified into six major groups, each with unique characteristics and roles in nature.

• Bacteria: Single-celled prokaryotes, found in various environments.

• Archaea: Prokaryotes distinct from bacteria, often found in extreme environments.

• Fungi: Eukaryotic organisms including yeasts and molds.

• Protozoa: Single-celled eukaryotes, often motile.

• Algae: Photosynthetic eukaryotes, both unicellular and multicellular.

• Viruses: Acellular entities, require host cells for replication.

Example: Escherichia coli (bacteria), Halobacterium (archaea), Saccharomyces cerevisiae (fungi).

Prokaryotic vs. Eukaryotic Organisms

Microorganisms are classified based on cellular structure.

• 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).

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 Debate

• Proponents: Aristotle, John Needham.

• Opponents: Francesco Redi, Lazzaro Spallanzani, Louis Pasteur.

Experiments: Redi's meat experiment, Needham's broth experiment, Spallanzani's sealed flask, Pasteur's swan-neck flask.

Major Scientists and Contributions

• Louis Pasteur: Disproved spontaneous generation, developed pasteurization.

• Robert Koch: Developed Koch's postulates for disease causation.

• Edward Jenner: Developed smallpox vaccine.

• Joseph Lister: Introduced antiseptic techniques.

Koch's Postulates

Four steps to prove the cause of an infectious disease:

1. Find the suspected agent in every case of the disease.

2. Isolate and grow the agent in pure culture.

3. Introduce the agent into a healthy host and observe the disease.

4. Re-isolate the agent from the experimental host.

Chapter 2: The Chemistry of Microbiology

Basic Chemical Concepts

• Matter: Anything that occupies space and has mass.

• Atom: Smallest unit of matter, composed of protons, neutrons, and electrons.

• Element: Pure substance consisting of one type of atom.

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

Atomic Structure

• Nucleus: Contains protons and neutrons.

• Electron Shells: Electrons orbit the nucleus in shells; first shell holds 2, second 8, third 8 electrons.

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

Chemical Bonds

• Nonpolar Covalent: Electrons shared equally.

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

• Ionic Bonds: Electrons transferred, forming cations (+) and anions (-).

Electronegativity: Determines bond polarity.

Hydrogen Bonds

Weak bonds between partially charged atoms, important for structure of water, proteins, and nucleic acids.

Chemical Reactions

• Synthesis: Building larger molecules.

• Decomposition: Breaking down molecules.

• Exchange: Rearranging atoms between molecules.

Endothermic: Absorbs energy. Exothermic: Releases energy.

Properties of Water

• Solvent for many substances.

• High heat capacity.

• Cohesion and adhesion.

• Participates in chemical reactions.

• Maintains temperature stability.

Acids, Bases, Salts, and Buffers

• Acids: Release H+ ions.

• Bases: Release OH- ions.

• Salts: Formed from acid-base reactions.

• Buffers: Stabilize pH in biological systems.

Organic Molecules

• Functional Groups: Specific groups of atoms that confer properties to organic molecules.

Lipids

• Triglycerides: Glycerol + 3 fatty acids.

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

• Waxes: Long-chain alcohol + fatty acid.

• Steroids: Four fused carbon rings.

Saturated: No double bonds. Unsaturated: One or more double bonds.

Carbohydrates

• Composed of C, H, O.

• Roles: Energy storage, structural support.

Proteins

• Functions: Enzymes, structural, transport, defense, regulation.

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

• Protein Structure Levels: Primary, secondary, tertiary, quaternary.

Nucleic Acids

• Nucleotide: Sugar, phosphate, nitrogenous base.

• DNA: Double-stranded, stores genetic information.

• RNA: Single-stranded, involved in protein synthesis.

Chapter 3: Cell Structure and Function

Major Processes of Living Cells

• Growth

• Reproduction

• Responsiveness

• Metabolism

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, simple structure.

• Eukaryotes: Nucleus, complex organelles.

Capsules vs. Slime Layers

• Capsule: Organized, firmly attached to cell wall.

• Slime Layer: Unorganized, loosely attached.

Bacterial Flagella

• Structure: Filament, hook, basal body.

• Arrangements: Monotrichous, lophotrichous, amphitrichous, peritrichous.

• Function: Motility.

Bacterial Shapes and Arrangements

• Shapes: Cocci (spherical), bacilli (rod-shaped), spirilla (spiral).

• Arrangements: Chains, clusters, pairs.

Peptidoglycan Structure

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

• Peptide Portion: Short amino acid chains cross-linking sugars.

Gram-Positive vs. Gram-Negative Cell Walls

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

• Gram-Negative: Thin peptidoglycan, outer membrane, stains pink.

Phospholipid Bilayer and Cytoplasmic Membrane

• Structure: Two layers of phospholipids.

• Significance: Selective permeability, barrier between cell and environment.

Fluid Mosaic Model

Describes membrane as a dynamic structure with proteins embedded in a flexible lipid bilayer.

Membrane Transport

• Passive: Diffusion, facilitated diffusion, osmosis.

• Active: Requires energy, e.g., active transport, group translocation.

Osmosis and Solution Types

• Osmosis: Movement of water across membrane.

• Isotonic: Equal solute concentration.

• Hypertonic: Higher solute outside cell.

• Hypotonic: Lower solute outside cell.

Bacterial Cytoplasm

• Contains DNA, ribosomes, inclusions.

Inclusions

• Storage granules, e.g., glycogen, polyphosphate.

Endospores

• Resistant structures formed by some bacteria for survival.

Ribosomes and Cytoskeleton

• Ribosomes: Protein synthesis.

• Cytoskeleton: Structural support.

Endosymbiotic Theory

Suggests mitochondria and chloroplasts originated from prokaryotic cells engulfed by ancestral eukaryotes.

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

Chapter 4: Microscopy, Staining, and Classification

Metric Units for Microbes

• Micrometer (µm) and nanometer (nm) are primary units.

• Order: meter > centimeter > millimeter > micrometer > nanometer.

Types of Microscopy

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

• Dark-field: Light reflects off specimen; enhances contrast for live, unstained samples.

• Phase: Uses phase shifts in light; reveals internal structures in living cells.

Electron Microscopy

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

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

Staining Techniques

• Simple Stains: Single dye, highlights cells.

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

• Special Stains: Flagella, negative stains.

Taxonomy and Classification

• Purpose: Organize and identify organisms.

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

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

• Linnaean System: Modified to include domains.

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

Procedures for Identification and Classification

• Physical characteristics

• Biochemical tests

• Serological tests

• Genetic analysis

• Phage typing