Microbiology Exam 1 Study Guide: Chapters 1-4

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Chapter 1 – Introduction to Microbiology

Definition and Scope of Microbiology

Microbiology is the study of organisms too small to be seen with the naked eye, including bacteria, archaea, viruses, fungi, protozoa, and algae. These organisms are collectively known as microbes and are characterized by their microscopic size and diverse metabolic capabilities.

Microorganisms include: Bacteria, archaea, viruses, fungi, protozoa, and microscopic algae.
Key characteristics: Unicellularity (most), rapid reproduction, and adaptability to diverse environments.

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.

Tenets: Mitochondria and chloroplasts have their own DNA, double membranes, and reproduce independently within the cell.
Evidence: Similarities in DNA sequences and ribosomes to certain bacteria.

History of the Microscope

Robert Hooke: First to describe cells (1665) using a compound microscope.
Antonie van Leeuwenhoek: Improved microscope lenses and was first to observe living microorganisms ("animalcules").

Golden Age of Microbiology

Theory of Biogenesis: Living organisms arise from pre-existing life (Pasteur).
Germ Theory of Disease: Microorganisms are the cause of many diseases (Koch, Pasteur).
Pasteur’s Swan-Necked Flask Experiment: Demonstrated that microorganisms do not arise spontaneously.
Koch’s Postulates: Criteria to establish a causative relationship between a microbe and a disease.
Aseptic Techniques: Semmelweis (handwashing), Lister (antiseptics), Nightingale (hospital sanitation).
Scientific Method Steps: Observation, hypothesis, experimentation, analysis, conclusion.
Epidemiology: Semmelweis (puerperal fever), Snow (cholera outbreak mapping).

Taxonomy and Classification

Eight Hierarchical Levels (Taxa): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Linnaeus’ Binomial Nomenclature: Genus and species names (e.g., Escherichia coli), italicized, genus capitalized, species lowercase.

Three Domains of Life

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

Symbiotic Relationships

Mutualism: Both partners benefit.
Commensalism: One benefits, the other is unaffected.
Parasitism: One benefits at the expense of the other.

Normal Microbiota

Definition: Microbes that colonize the body without causing disease.
Locations: Skin, gut, respiratory tract, urogenital tract.
Effects: Aid digestion, protect against pathogens, stimulate immune system.

Biofilms

Definition: Structured communities of microbes attached to surfaces and embedded in a self-produced matrix.
Advantages: Protection from environmental stress, antibiotics, and immune responses.

Growth Media and Isolation Techniques

Growth Media: Nutrient-rich substances for culturing microbes (e.g., agar plates, broths).
Streak Plate Technique: Method to isolate pure colonies by spreading cells over an agar surface.

Staining and Microscopy

Staining Types: Simple, differential (e.g., Gram stain), and special stains (e.g., endospore, capsule).
Compound Light Microscope: Uses visible light and multiple lenses to magnify specimens.
Alternative Microscopy: Phase-contrast, fluorescence, electron microscopy (TEM, SEM).

Chapter 2 – Biochemistry Basics

Atoms, Ions, Isotopes, and Molecules

Atom: Smallest unit of an element, composed of protons, neutrons, and electrons.
Ion: Atom with a net charge due to loss/gain of electrons.
Isotope: Atoms of the same element with different numbers of neutrons.
Molecule: Two or more atoms bonded together.
Atomic Number: Number of protons in the nucleus.
Atomic Mass: Sum of protons and 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: Substance that donates H+ ions.
Base: Substance that accepts H+ ions or donates OH-.
Salt: Compound formed from acid-base reactions.
pH Scale: Measures H+ concentration; ranges from 0 (acidic) to 14 (basic), 7 is neutral.

Chemical Bonding

Ionic Bonds: Transfer of electrons between atoms (e.g., NaCl).
Covalent Bonds: Sharing of electrons (e.g., H2O).
Hydrogen Bonds: Weak attraction between polar molecules.
Van der Waals Interactions: Weak, transient attractions between molecules.

Polarity, Hydrophilicity, Hydrophobicity, Amphipathicity

Polarity: Unequal sharing of electrons, leading to partial charges.
Hydrophilic: Water-loving, dissolves in water.
Hydrophobic: Water-fearing, does not dissolve in water.
Amphipathic: Contains both hydrophilic and hydrophobic regions (e.g., phospholipids).

Chemical Reactions and Enzymes

Chemical Reaction: Process that changes substances into different substances.
Catalysis: Acceleration of a reaction by a catalyst (often an enzyme).
Enzymes: Biological catalysts that lower activation energy.
Activation Energy Equation:

Reversibility and Equilibrium: Many reactions are reversible and reach a state where forward and reverse rates are equal.

Macromolecules

Carbohydrates: Sugars and starches; energy storage and structural roles.
Lipids: Fats, oils, phospholipids; energy storage, membrane structure.
Nucleic Acids: DNA and RNA; genetic information storage and transfer.
Proteins: Enzymes, structural components, signaling molecules.

Chapter 3 – Introduction to Prokaryotic Cells

Three Domains and Their Characteristics

Bacteria: Unicellular, peptidoglycan cell walls, diverse metabolism.
Archaea: Unicellular, unique membrane lipids, often extremophiles.
Eukaryotes: Unicellular or multicellular, membrane-bound organelles.

Prokaryotic Description and Morphology

Colony Characteristics: Size, elevation, margins, color.
Cell Morphology: Shapes (coccus, bacillus, spirillum) and arrangements (chains, clusters).

Binary Fission

Steps: DNA replication, chromosome segregation, cell elongation, septum formation, cell division.

Extracellular Structures

Capsule: Polysaccharide layer for protection and adhesion.
Cell Wall: Provides shape and protection; peptidoglycan in bacteria.
Plasma Membrane: Selective barrier for transport.
Flagella: Motility structures.
Fimbriae: Attachment to surfaces.
Pili: DNA transfer (conjugation) and attachment.

Membrane Transport in Prokaryotes

Simple Diffusion: Movement down concentration gradient without energy.
Osmosis: Diffusion of water across a membrane.
Facilitated Diffusion: Transport via membrane proteins, no energy required.
Active Transport: Movement against gradient, requires energy (ATP).

Intracellular Structures

Cytoplasm: Gel-like matrix inside the cell.
DNA/Nucleoid: Genetic material, usually a single circular chromosome.
Cytoskeleton: Protein filaments for shape and division.
Ribosomes: Protein synthesis machinery (70S in prokaryotes).
Inclusion Bodies: Storage of nutrients and compounds.
Endospores: Dormant, resistant structures for survival in harsh conditions.

Chapter 4 – Introduction to Eukaryotic Cells

Endosymbiotic Theory and Organelle Origins

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

Cell Division and Reproduction

Binary Fission: Prokaryotic cell division.
Mitosis: Eukaryotic asexual division, produces identical cells.
Meiosis: Eukaryotic sexual division, produces gametes with half the chromosome number.
Comparison: Binary fission is simpler and faster; mitosis and meiosis involve complex chromosome movements.

Membrane Transport in Eukaryotes

Simple Diffusion: Passive movement down gradient.
Facilitated Diffusion: Passive, via transport proteins.
Active Transport: Requires energy; primary uses ATP, secondary uses ion gradients.
Endocytosis: Uptake of materials via vesicles.
Phagocytosis: "Cell eating" of large particles.
Pinocytosis: "Cell drinking" of fluids.
Receptor-Mediated Endocytosis: Specific uptake via receptors.

Four Eukaryotic Kingdoms

Kingdom	Characteristics	Examples	Microbial?	Role in Disease
Animalia	Multicellular, no cell walls	Humans, worms	No	Some parasitic worms
Plantae	Multicellular, cell walls, photosynthetic	Algae, plants	Some algae	Rarely pathogenic
Fungi	Unicellular/multicellular, chitin cell walls	Yeasts, molds	Yes	Pathogenic fungi (e.g., Candida)
Protists	Unicellular/multicellular, diverse	Protozoa, algae, slime molds	Yes	Pathogenic protozoa (e.g., Plasmodium)

Extracellular Structures in Eukaryotes

Glycocalyx: Carbohydrate-rich layer for protection and adhesion.
Cell Walls: Found in plants, fungi, algae; provide structure.
Plasma Membrane: Phospholipid bilayer with embedded proteins.
Flagella: Long, whip-like structures for movement.
Cilia: Short, numerous projections for movement or fluid flow.

Intracellular Structures in Eukaryotes

Ribosomes: Protein synthesis (80S in eukaryotes).
Cytoskeleton: Microtubules, microfilaments, intermediate filaments for shape and transport.
Centrosome: Microtubule organizing center.
Nucleus: Contains genetic material, site of transcription.
Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes, protein synthesis.
- Smooth ER: Lipid synthesis, detoxification.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
Transport Vesicles: Move materials between organelles.
Lysosomes: Digestive enzymes for breakdown of macromolecules.
Peroxisomes: Breakdown of fatty acids and detoxification.
Vacuoles: Storage and structural support (large in plants).
Mitochondria: ATP production via cellular respiration.
Chloroplasts: Photosynthesis in plants and algae.

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