Microbiology Exam 1 Study Guide: Chapters 1-4

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Chapter 1 – Introduction to Microbiology

What is Microbiology?

Microbiology is the study of microscopic organisms, including bacteria, archaea, viruses, fungi, protozoa, and algae. These organisms are characterized by their small size, diversity, and roles in ecosystems, health, and disease.

Microorganisms include prokaryotes (bacteria, archaea) and eukaryotes (fungi, protozoa, algae).
Viruses and prions are also studied in microbiology, though they are acellular.

Endosymbiotic Theory

The endosymbiotic theory explains the origin of eukaryotic organelles such as mitochondria and chloroplasts, proposing that these organelles originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Evidence includes double membranes, their own DNA, and similarities to bacteria.

History of the Microscope

Robert Hooke: First to describe cells (1665).
Antonie van Leeuwenhoek: First to observe living microorganisms (1670s).

Golden Age of Microbiology

Theory of Biogenesis: Life arises from pre-existing life (Louis Pasteur).
Germ Theory of Disease: Microorganisms cause disease (Pasteur, Koch).
Pasteur’s Swan-Necked Flask Experiment: Disproved spontaneous generation.
Koch’s Postulates: Criteria to establish a causative relationship between a microbe and a disease.
Aseptic Techniques: Semmelweis (handwashing), Lister (antiseptics), Nightingale (nursing hygiene).
Scientific Method: Observation, hypothesis, experiment, analysis, conclusion.
Epidemiology: Semmelweis (puerperal fever), Snow (cholera outbreak mapping).

Taxonomy and Classification

Eight hierarchical levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Linnaeus’ Binomial Nomenclature: Genus species (italicized or underlined), Genus capitalized, species lowercase (e.g., Escherichia coli).

Three Domains of Life

Bacteria: Prokaryotic, peptidoglycan cell walls.
Archaea: Prokaryotic, unique membrane lipids, often extremophiles.
Eukarya: Eukaryotic, includes animals, plants, fungi, protists.

Symbiotic Relationships

Mutualism, commensalism, parasitism.

Normal Microbiota

Microbes normally present in/on the body; contribute to health, can cause disease if displaced.

Biofilms

Communities of microorganisms attached to surfaces, embedded in extracellular matrix.
Advantages: protection, nutrient access, resistance to antimicrobials.

Growth Media and Isolation Techniques

Growth Media: Nutrient solutions (broth, agar plates) for culturing microbes.
Streak Plate Technique: Isolates pure colonies.

Staining and Microscopy

Staining Types: Simple, differential (Gram, acid-fast), special stains.
Compound Light Microscope: Uses visible light, multiple lenses.
Alternative Microscopy: Phase-contrast, fluorescence, electron microscopy.

Chapter 2 – Biochemistry Basics

Atoms, Ions, Isotopes, and Molecules

Atom: Smallest unit of an element.
Ion: Charged atom (cation: +, anion: -).
Isotope: Atoms of the same element with different numbers of neutrons.
Molecule: Two or more atoms bonded together.
Atomic Number: Number of protons.
Atomic Mass: Protons + neutrons.
Organic Molecules: Contain carbon-hydrogen bonds (e.g., glucose).
Inorganic Molecules: Do not contain C-H bonds (e.g., water, salts).

Acids, Bases, Salts, and the pH Scale

Acid: Donates H+ ions (pH < 7).
Base: Accepts H+ ions (pH > 7).
Salt: Ionic compound from acid-base reaction.
pH Scale: Measures H+ concentration; logarithmic scale from 0 (acidic) to 14 (basic).

Chemical Bonding

Ionic Bonds: Transfer of electrons between atoms.
Covalent Bonds: Sharing of electrons.
Hydrogen Bonds: Weak attraction between polar molecules.
Van der Waals Interactions: Weak, transient attractions.
Valence Electrons: Electrons in the outer shell; determine bonding.

Polarity, Hydrophilicity, Hydrophobicity, Amphipathicity

Polarity: Unequal sharing of electrons; polar molecules dissolve in water.
Hydrophilic: Water-loving; dissolves in water.
Hydrophobic: Water-fearing; does not dissolve in water.
Amphipathic: Both hydrophilic and hydrophobic regions (e.g., phospholipids).

Chemical Reactions and Enzymes

Catalysis: Enzymes lower activation energy, speeding up reactions.
Activation Energy: Energy required to start a reaction.
Reversibility: Many reactions are reversible; equilibrium is when forward and reverse rates are equal.

= Activation energy

Macromolecules

Carbohydrates: Sugars and polysaccharides; energy and structure (e.g., glucose, cellulose).
Lipids: Fats, phospholipids, steroids; energy storage, membranes.
Nucleic Acids: DNA, RNA; genetic information.
Proteins: Amino acid polymers; enzymes, structure, transport.

Chapter 3 – Introduction to Prokaryotic Cells

Three Domains of Life

Bacteria: Peptidoglycan cell walls, diverse metabolism.
Archaea: Unique lipids, extremophiles, no peptidoglycan.
Eukaryotes: Membrane-bound organelles.

Prokaryotic Description

Colony Morphology: Size, elevation, margin, color.
Cell Morphology: Shape (coccus, bacillus, spirillum), arrangement (chains, clusters).

Binary Fission

Prokaryotic cell division; DNA replicates, cell elongates, septum forms, two daughter cells produced.

Extracellular Structures

Capsule: Polysaccharide layer; protection, adherence.
Cell Wall: Structure, prevents lysis.
Plasma Membrane: Selective barrier.
Flagella: Motility.
Fimbriae: Attachment.
Pili: DNA transfer (conjugation).

Membrane Transport

Simple Diffusion: Passive, down concentration gradient.
Osmosis: Diffusion of water.
Facilitated Diffusion: Passive, via transport proteins.
Active Transport: Requires energy (ATP), against gradient.

Intracellular Structures

Cytoplasm: Gel-like interior.
DNA/Nucleoid: Genetic material.
Cytoskeleton: Shape, division.
Ribosomes: Protein synthesis.
Inclusion Bodies: Storage.
Endospores: Dormant, resistant structures.

Chapter 4 – Introduction to Eukaryotic Cells

Endosymbiotic Theory and Organelle Evolution

Mitochondria and chloroplasts originated from engulfed prokaryotes.
Evidence: Double membranes, own DNA, ribosomes similar to bacteria.

Cell Division and Reproduction

Binary Fission: Prokaryotes.
Mitosis: Eukaryotic asexual division; identical daughter cells.
Meiosis: Eukaryotic sexual division; genetic diversity.

Membrane Transport in Eukaryotes

Simple Diffusion: Small, nonpolar molecules.
Facilitated Diffusion: Via channels/carriers.
Active Transport: Primary (ATP-driven), secondary (ion gradients).
Endocytosis: Uptake of large particles.
Phagocytosis: "Cell eating" (solids).
Pinocytosis: "Cell drinking" (liquids).
Receptor-Mediated Endocytosis: Specific uptake via receptors.

Four Eukaryotic Kingdoms

Kingdom	Characteristics	Microbial?	Human Disease?
Animalia	Multicellular, no cell walls	No	Some parasites
Plantae	Multicellular, cell walls, photosynthetic	No	Rare
Fungi	Unicellular/multicellular, chitin cell walls	Some	Yes (mycoses)
Protists	Unicellular/multicellular, diverse	Many	Yes (malaria, amoebiasis)

Extracellular Structures

Glycocalyx: Polysaccharide coating; protection, adhesion.
Cell Walls: Structure, varies by kingdom (plants: cellulose, fungi: chitin).
Plasma Membrane: Phospholipid bilayer.
Flagella: Motility (different structure from prokaryotes).
Cilia: Short, numerous, movement.

Intracellular Structures

Ribosomes: Protein synthesis (80S in eukaryotes).
Cytoskeleton: Shape, movement.
Centrosome: Microtubule organization.
Nucleus: Contains DNA.
Endoplasmic Reticulum: Rough (ribosomes, protein synthesis), Smooth (lipid synthesis).
Golgi Apparatus: Modifies, sorts, packages proteins/lipids.
Transport Vesicles: Move materials.
Lysosomes: Digestive enzymes.
Peroxisomes: Break down fatty acids, detoxify.
Vacuoles: Storage.
Mitochondria: ATP production.
Chloroplasts: Photosynthesis (plants, algae).

Additional info: Eukaryotic cells are generally larger and more complex than prokaryotic cells, with compartmentalized functions due to organelles.