Microbiology Core Concepts: Mini-Textbook Study Notes

Chapter 1 – Microbes Overview

1. Ways Microbes Affect Life

Microorganisms play essential roles in ecosystems and human health. They can be beneficial or harmful.

• Digestion: Aid in breaking down food in the gut.

• Vitamin/Food Production: Synthesize vitamins and help produce foods (e.g., cheese, bread).

• Nutrient Recycling: Decompose organic matter, recycling nutrients.

• Drug Production: Used to produce antibiotics and other drugs.

• Disease Causation: Some microbes cause infectious diseases.

2. Scientific Nomenclature

Microbes are named using the binomial system, which includes genus and species.

• Genus: Capitalized and italicized (e.g., Escherichia).

• Species: Lowercase and italicized (e.g., coli).

3. Major Groups of Microorganisms

• Bacteria

• Archaea

• Fungi

• Protozoa

• Algae

• Viruses

• Helminths (parasitic worms)

4. Historical Contributions

• van Leeuwenhoek: First to observe microbes.

• Pasteur: Disproved spontaneous generation, developed pasteurization, fermentation studies.

• Lister: Introduced antiseptic surgery.

• Koch: Developed postulates for linking microbes to disease.

• Jenner: Developed smallpox vaccine.

• Fleming: Discovered penicillin.

5. Beneficial Activities

• Food production (e.g., bread, cheese)

• Antibiotics

• Recycling nutrients

• Nitrogen fixation

• Sewage treatment

6. Infectious Diseases (Examples)

• Tuberculosis (TB)

• Malaria

• Influenza

• COVID-19

7. Emerging Infectious Diseases

• New or changing diseases, increasing in incidence (e.g., Ebola, Zika, SARS-CoV-2)

Chapter 2 – Chemistry

1. Atom Structure

Atoms are the basic units of matter, composed of protons (+), neutrons (0), and electrons (–).

• Protons: Positive charge, found in nucleus.

• Neutrons: Neutral charge, found in nucleus.

• Electrons: Negative charge, orbit nucleus; determine chemical reactivity.

2. Bonds

• Ionic: Transfer of electrons.

• Covalent: Sharing of electrons.

• Hydrogen: Weak attraction between molecules.

3. Properties of Water

• Polar molecule, excellent solvent.

• High heat capacity, cohesion, adhesion.

4. Organic vs Inorganic Compounds

• Organic: Carbon-based (proteins, sugars).

• Inorganic: Water, salts.

5. Building Blocks

• Carbohydrates: Monosaccharides.

• Lipids: Glycerol + fatty acids.

• Phospholipids: Glycerol + fatty acids + phosphate.

• Proteins: Amino acids.

• Nucleic acids: Nucleotides.

6. ATP Role

• Main energy carrier; stores and transfers energy.

Chapter 3 – Microscopy & Stains

1. Light Path

Describes how light travels through a microscope to the eye.

• Light → condenser → specimen → objective lens → ocular lens → eye

2. Magnification & Resolution

• Total Magnification: Ocular × objective lens.

• Resolution: Ability to distinguish two points as separate.

3. Uses of Microscopes

• Brightfield: Stained specimens.

• Darkfield: Living, unstained microbes.

• Phase Contrast: Internal structures.

• Fluorescence: UV light, fluorescent dyes.

4. Electron vs Light Microscope

• Electron: Uses beams of electrons, higher resolution.

• Light: Uses light, lower resolution.

5. TEM vs SEM

• TEM (Transmission Electron Microscope): Views internal cell structures.

• SEM (Scanning Electron Microscope): Views surface structures.

6. Acids vs Basic Dyes

• Acidic: Stains background.

• Basic: Stains cells.

7. Staining Types

• Simple: One dye.

• Differential: Gram/acid-fast.

• Special: Capsule, spore, flagella.

8. Gram Stain Steps

1. Crystal violet = purple both.

2. Iodine = fix.

3. Alcohol = Gram+ purple, Gram– clear.

4. Safranin = Gram– pink.

9. Gram vs Acid-Fast

• Gram+: Thick peptidoglycan cell wall.

• Acid-fast: Stains waxy Mycobacterium cell wall.

10. Special Stains

• Capsule: Halo appearance.

• Endospore: Green spores.

• Flagella: Makes flagella visible.

Chapter 4 – Prokaryotes & Eukaryotes

1. Comparison

• Prokaryote: No nucleus or organelles.

• Eukaryote: Has nucleus and organelles.

2. Shapes

• Cocci (spherical)

• Bacilli (rod-shaped)

• Spirals

3. Structures

• Glycocalyx: Protection, attachment.

• Flagella: Movement (axial filaments = corkscrew motion).

• Fimbriae: Attachment.

• Pili: DNA transfer.

4. Gram Wall Differences

• Gram+: Thick peptidoglycan.

• Gram–: Thin, outer membrane, LPS toxin.

5. Wall-Less Forms

• Protoplast: Wall-less Gram+.

• Spheroplast: Wall-less Gram–.

• L form: Naturally wall-less.

6. Cell Membrane

• Phospholipid bilayer, selective barrier, enzymes for energy.

7. Transport

• Simple diffusion, osmosis, facilitated diffusion, active transport.

8. Internal Structures

• Nuclear area (DNA)

• Ribosomes (protein synthesis)

• Inclusions (storage)

9. Endospores

• Resistant structures: Sporulation = formation, Germination = growth.

10. Endosymbiotic Theory

• Mitochondria/chloroplasts from ancient bacteria.

Chapter 5 – Metabolism

1. Metabolism

• Anabolism: Build molecules, requires energy.

• Catabolism: Break molecules, releases energy.

2. ATP Role

• Transfers energy from catabolism to anabolism.

3. Enzyme Components

• Apoenzyme: Protein part.

• Cofactor: Nonprotein part.

4. Reaction Mechanism

• Substrate binds to enzyme, enzyme changes shape, product released.

5. Redox

• Oxidation: Lose electrons.

• Reduction: Gain electrons.

6. Enzyme Types

• Competitive: Inhibitor binds active site.

• Noncompetitive: Inhibitor binds elsewhere.

7. Biochemical Pathways

• Stepwise reactions that make/break molecules.

8. Glycolysis

• Glucose → 2 pyruvate + 2 ATP + NADH.

$\text{Glucose} \rightarrow 2\ \text{Pyruvate} + 2\ \text{ATP} + 2\ \text{NADH}$

9. Krebs Cycle

• Pyruvate → CO2 + NADH + FADH2 + ATP.

$\text{Pyruvate} \rightarrow \text{CO}_2 + \text{NADH} + \text{FADH}_2 + \text{ATP}$

10. Chemiosmosis

• ETC pumps H+, ATP synthase makes ATP.

11. Respiration

• Aerobic: O2 final electron acceptor (lots ATP).

• Anaerobic: Non-O2 acceptors (less ATP).

12. Fermentation

• Organic acceptor, produces alcohol/acid, little ATP.

13. Lipid/Protein Degradation

• Lipids → fatty acids + Krebs.

• Proteins → amino acids + Krebs.

14. Photosphorylation

• Cyclic (ATP only), non-cyclic (ATP + NADPH).

15. Photosynthesis

• Light-dependent = ATP + NADPH.

• Light-independent = sugars (Calvin cycle).

16. Energy in Bacteria

• Energy from catabolism used for biosynthesis, motility, transport.

17. Nutritional Types

• Photoautotroph, photoheterotroph, chemoautotroph, chemoheterotroph.

Chapter 6 – Microbial Growth

1. Temperature Groups

• Psychrophiles: Cold-loving.

• Psychrotrophs: Fridge temperatures.

• Mesophiles: Moderate temperatures (pathogens).

• Thermophiles: Heat-loving.

• Hyperthermophiles: Very hot environments.

2. Osmotic Pressure

• Salt/sugar preserve food; halophiles tolerate salt.

3. Nutrients

• Macro: C, N, O, P.

• Trace: Fe, Zn, Cu.

• Organic growth factors: Vitamins, amino acids.

4. Oxygen Requirements

• Obligate aerobe: Needs oxygen.

• Obligate anaerobe: Oxygen is toxic.

• Facultative anaerobe: Can use oxygen or not.

• Microaerophile: Needs low oxygen.

• Aerotolerant: Tolerates oxygen, does not use it.

5. Enzymes for Oxygen

• Aerobes have SOD (superoxide dismutase), catalase.

• Anaerobes lack these enzymes.

6. Colony & Pure Culture

• Colony = visible cluster.

• Pure culture isolated by streak plate.

7. Growth & Binary Fission

• Growth = increase in cell number.

• Binary fission: 1 cell divides into 2 identical cells.

8. Growth Phases

• Lag → Log → Stationary → Death.

9. Direct Methods

• Plate counts, filtration, direct microscopic count.

10. Direct vs Indirect

• Direct: Actual cell counts.

• Indirect: Turbidity, metabolic activity, dry weight.

Chapter 7 – Microbial Control

1. Terms

• Sterilization: All microbes destroyed.

• Disinfection: Surfaces.

• Antisepsis: Living tissue.

• Degerming: Removal of microbes.

• Sanitization: Safe levels.

• Bacteriostasis: Stops growth.

• Asepsis: No contamination.

2. Death Pattern

• Constant rate, not all at once.

3. Targets

• Membranes, proteins, nucleic acids.

4. Heat Methods

• Moist heat (boil, autoclave, pasteurize) better than dry heat (oven, flaming).

5. Other Methods

• Filtration, cold, pressure, drying, osmotic pressure.

6. Radiation

• UV = DNA damage.

• Ionizing = DNA breaks.

7. Factors in Disinfection

• Concentration, time, pH, organic matter, microbe type.

8. Tests

• Use-dilution = effectiveness in solution.

• Filter paper = zone of inhibition.

9. Chemical Disinfectants

• Phenols, alcohol, halogens, heavy metals, aldehydes.

10. Resistance

• Endospores > Mycobacteria > Gram– > Gram+.

Chapter 8 & 9 – Genetics

1. Key Terms

• Genetics: Study of heredity.

• Genome: All DNA in a cell.

• Gene: DNA code for a product.

• Chromosome: DNA molecule.

• Plasmid: Extra DNA.

• Genotype: Genes present.

• Phenotype: Traits expressed.

• Genetic code: Rules for translation.

• Genomics: Study of whole genomes.

2. DNA Replication

• Semi-conservative: Old strand + new strand.

3. Protein Synthesis

• Transcription: DNA → mRNA.

• Translation: mRNA → protein.

4. Gene Regulation

• Induction: Turns gene on.

• Repression: Turns gene off.

5. Mutations

• Point, insertion, deletion. Prevention by DNA repair.

6. Mutagens

• Chemicals, radiation causing mutations.

7. Repair

• Light repair, excision repair.

8. Mutagen Effect

• Increase mutation rate.

9. Ames Test

• Tests chemical mutagenicity using bacteria.

10. Gene Transfer

• Vertical: Parent to offspring.

• Horizontal: Between cells.

11. Horizontal Transfer Methods

• Transformation: Uptake of DNA.

• Conjugation: Pili-mediated transfer.

• Transduction: Virus-mediated transfer.

12. Plasmids & Transposons

• Plasmids: Resistance, toxins.

• Transposons: "Jumping genes".

Chapter 13 – Viruses

1. Virus vs Bacteria

• Virus: Nonliving, needs host, DNA/RNA + protein coat.

• Bacteria: Living cells.

2. Structure

• Nonenveloped: Nucleic acid + capsid.

• Enveloped: Capsid + lipid envelope.

3. Viral Species Example

• Family: Herpesviridae

• Genus: Simplexvirus

• Common name: HSV-1

4. Phage Culture

• On bacterial lawns → plaques.

5. Animal Virus Culture

• In eggs, tissue culture.

6. Lytic Cycle

• Attachment → penetration → biosynthesis → assembly → release.

7. Lysogenic Cycle

• Viral DNA integrates into host genome, later can enter lytic cycle.

8. DNA vs RNA Animal Viruses

• DNA viruses replicate in nucleus.

• RNA viruses replicate in cytoplasm.

9. Oncogenes

• Viral genes that cause cancer; transformed cell = cancerous.

10. Persistent vs Latent Viruses

• Persistent: Long-term, continuous infection.

• Latent: Hidden, reactivates.

11. Virus vs Viroid vs Prion

• Virus: Nucleic acid + protein.

• Viroid: Naked RNA.

• Prion: Misfolded protein.