Microbiology Exam 1 Study Guide: Chapters 1, 3, 4, 6, 7

Ch. 1 – The Microbial World and You

1. Microbes and Their Impact

• Microbes are microscopic organisms, including bacteria, viruses, fungi, protozoa, and algae.

• They play destructive roles (causing disease, food spoilage) and beneficial roles (decomposition, fermentation, biotechnology, and maintaining environmental balance).

• Examples: Lactobacillus in yogurt production (beneficial); Streptococcus pyogenes causing strep throat (destructive).

2. Scientific Nomenclature

• The binomial nomenclature system assigns each organism a two-part name: Genus (capitalized) and specific epithet (lowercase), both italicized (e.g., Escherichia coli).

• The genus groups closely related species; the specific epithet identifies the species within the genus.

3. Major Groups of Microorganisms

• Bacteria and Archaea are prokaryotes (no nucleus).

• Fungi, protozoa, algae, and helminths are eukaryotes (nucleus present).

• Viruses are acellular and require host cells to reproduce.

4. The Three Domains

• The three domains are Bacteria, Archaea, and Eukarya.

5. Historical Contributions

• Hooke observed cells in cork, leading to cell theory (all living things are composed of cells).

• van Leeuwenhoek first observed live microorganisms.

6. Spontaneous Generation vs. Biogenesis

• Spontaneous generation: Life arises from nonliving matter (disproven).

• Biogenesis: Life arises from pre-existing life.

• Evidence: Pasteur’s swan-neck flask experiment disproved spontaneous generation.

7. Key Figures in Microbiology

• Needham: Supported spontaneous generation.

• Spallanzani: Disproved spontaneous generation with sealed flasks.

• Virchow: Proposed biogenesis.

• Pasteur: Disproved spontaneous generation, developed pasteurization.

8. Germ Theory of Disease

• Pasteur influenced Lister (aseptic surgery) and Koch (Koch’s postulates).

• Germ theory: Microorganisms cause disease.

9. Koch’s Postulates

• Set of criteria to prove a specific microbe causes a specific disease.

10. Jenner’s Discovery

• Developed the first vaccine (smallpox) using cowpox virus.

11. Ehrlich and Fleming

• Ehrlich: Developed “magic bullet” (selective drug, e.g., Salvarsan for syphilis).

• Fleming: Discovered penicillin (first antibiotic).

12. Subfields of Microbiology

• Bacteriology: Study of bacteria.

• Mycology: Study of fungi.

• Parasitology: Study of parasites.

• Immunology: Study of immunity.

• Virology: Study of viruses.

13. Microbial Genetics and Molecular Biology

• Microbial genetics: Study of heredity in microbes.

• Molecular biology: Study of DNA, RNA, and protein synthesis.

14. Beneficial Activities of Microorganisms

• Decomposition, nitrogen fixation, food production, biotechnology.

15. Biotechnology and Recombinant DNA Technology

• Biotechnology: Use of microbes to produce foods and chemicals.

• Recombinant DNA technology: Genetic engineering to modify organisms.

• Examples: Insulin production (recombinant); fermentation (traditional biotechnology).

16. Normal Microbiota and Resistance

• Normal microbiota: Microbes normally present in/on the body.

• Resistance: Ability to ward off disease.

17. Biofilms

• Biofilm: Community of microbes attached to a surface.

• Important in infections and industrial settings.

18. Emerging Infectious Diseases

• New or changing diseases increasing in incidence.

• Factors: Evolution, travel, ecological changes.

Ch. 3 – Observing Microorganisms Through a Microscope

1. Metric Units of Measurement

• Microorganisms are measured in micrometers (μm) and nanometers (nm).

• 1 μm = 1,000 nm.

• Example: 10 μm = 10,000 nm.

2. Compound Microscope Pathway

• Light passes through the condenser lens, specimen, objective lens, and ocular lens.

3. Magnification and Resolution

• Total magnification: Objective lens × ocular lens.

• Resolution: Ability to distinguish two points as separate; e.g., 0.2 nm means two points 0.2 nm apart can be distinguished.

4. Types of Microscopy

• Brightfield: Standard illumination.

• Darkfield: Highlights unstained specimens.

• Phase-contrast: Enhances contrast in transparent specimens.

• Differential interference contrast: 3D appearance.

• Fluorescence: Uses fluorescent dyes.

• Confocal: 3D images using lasers.

• Two-photon: Deep tissue imaging.

• Scanning acoustic: Uses sound waves.

5. Electron vs. Light Microscopy

• Electron microscopes use electrons, have higher resolution than light microscopes.

6. Types of Electron Microscopy

• TEM (Transmission Electron Microscopy): Internal structures.

• SEM (Scanning Electron Microscopy): Surface structures.

• Scanned-probe: Surface at atomic level.

7. Staining Techniques

• Acidic dyes: Stain background (negative stain).

• Basic dyes: Stain cells.

• Simple stain: Highlights entire organism.

• Fixing: Preserves and attaches cells to slide.

8. Differential Stains

• Gram stain: Differentiates gram-positive (purple) and gram-negative (pink) bacteria.

• Acid-fast stain: Identifies Mycobacterium and Nocardia.

9. Special Stains

• Capsule stain: Visualizes capsules.

• Endospore stain: Detects endospores (appear green when stained).

• Flagella stain: Visualizes flagella.

Ch. 4 – Functional Anatomy of Prokaryotic and Eukaryotic Cells

1. Prokaryotes vs. Eukaryotes

• Prokaryotes: No nucleus, no membrane-bound organelles.

• Eukaryotes: Nucleus, membrane-bound organelles.

2. Bacterial Shapes

• Coccus (spherical), Bacillus (rod-shaped), Spiral (spirillum, spirochete, vibrio).

• Streptococci: Chains of cocci.

3. Glycocalyx

• Gelatinous outer covering; capsule (organized) or slime layer (unorganized).

• Capsules prevent phagocytosis (medically important).

4. Surface Structures

• Flagella: Motility.

• Axial filaments: Movement in spirochetes.

• Fimbriae: Attachment.

• Pili: DNA transfer (conjugation).

5. Cell Walls

• Gram-positive: Thick peptidoglycan, teichoic acids.

• Gram-negative: Thin peptidoglycan, outer membrane, lipopolysaccharide (LPS).

• Acid-fast: Mycolic acid (e.g., Mycobacterium).

• Archaea: No peptidoglycan.

• Mycoplasmas: No cell wall; resistant to antibiotics targeting cell wall synthesis.

6. Protoplasts, Spheroplasts, and L Forms

• Protoplast: Gram-positive cell without cell wall.

• Spheroplast: Gram-negative cell with partial cell wall removal.

• L forms: Bacteria that have lost cell wall, can revert.

7. Plasma Membrane

• Phospholipid bilayer; selective permeability.

• Injury by alcohols, detergents, antibiotics (e.g., polymyxin).

8. Transport Mechanisms

• Simple diffusion: Movement down concentration gradient.

• Facilitated diffusion: Uses transport proteins.

• Osmosis: Water movement across membrane.

• Active transport: Requires energy (ATP).

• Group translocation: Substance chemically modified during transport.

9. Internal Structures

• Nucleoid: DNA location in prokaryotes.

• Ribosomes: Protein synthesis (70S in prokaryotes, 80S in eukaryotes).

• Inclusions: Storage granules (e.g., polysaccharide, lipid, sulfur).

• Endospores: Dormant, resistant structures formed under stress.

10. Eukaryotic Cell Structures

• Flagella and cilia: 9+2 microtubule arrangement.

• Cell walls: Cellulose (plants), chitin (fungi), none in animals.

• Plasma membrane: Contains sterols.

• Cytoplasm: Contains cytoskeleton, organelles.

• Ribosomes: 80S (cytoplasm), 70S (mitochondria, chloroplasts).

Ch. 6 – Microbial Growth

1. Temperature Groups

• Psychrophiles: Cold-loving.

• Mesophiles: Moderate temperature.

• Thermophiles: Heat-loving.

• Hyperthermophiles: Grow above 80°C, often in oceanic depths.

2. pH and Growth

• Most bacteria grow best at pH 6.5–7.5.

• Buffers (e.g., phosphate salts) maintain pH stability.

3. Osmotic Pressure

• High salt/sugar inhibits growth (food preservation).

4. Chemical Requirements

• Carbon: Structural backbone.

• Nitrogen: Proteins, nucleic acids.

• Sulfur: Amino acids, vitamins.

• Phosphorus: Nucleic acids, ATP.

5. Oxygen Requirements

• Obligate aerobes: Require O2.

• Facultative anaerobes: Grow with or without O2.

• Obligate anaerobes: Cannot tolerate O2.

• Aerotolerant anaerobes: Tolerate O2, do not use it.

• Microaerophiles: Require low O2.

6. Toxic Oxygen

• Enzymes (superoxide dismutase, catalase) detoxify reactive oxygen species.

7. Biofilms

• Microbes form communities (biofilms) on surfaces; increase resistance to antibiotics and immune response.

8. Culture Media

• Chemically defined: Exact composition known.

• Complex: Contains extracts, composition varies.

9. Special Culture Techniques

• Anaerobic techniques: Remove O2.

• Living host cells: For obligate intracellular microbes.

• Candle jars: Increase CO2.

• Selective media: Suppress unwanted microbes.

• Differential media: Distinguish colonies.

• Enrichment media: Favor growth of specific microbes.

10. Biosafety Levels

• BSL-1: Basic, non-pathogenic microbes.

• BSL-2: Moderate risk.

• BSL-3: Aerosol transmission risk.

• BSL-4: High risk, dangerous pathogens.

11. Colonies and Pure Cultures

• Colony: Visible mass of cells from one cell.

• Streak plate method: Isolates pure cultures.

12. Preservation Methods

• Deep-freezing: -50°C to -95°C.

• Lyophilization: Freeze-drying.

13. Bacterial Growth and Division

• Binary fission: Cell divides into two.

• Generation time: Time for population to double.

14. Growth Phases

• Lag phase: Adaptation.

• Log phase: Exponential growth.

• Stationary phase: Growth = death.

• Death phase: Decline.

15. Measuring Growth

• Direct methods: Plate count, filtration, MPN, direct microscopic count.

• Indirect methods: Turbidity, metabolic activity, dry weight.

Ch. 7 – The Control of Microbial Growth

1. Key Terms

• Sterilization: Removal of all microbial life.

• Disinfection: Destruction of pathogens.

• Antisepsis: Destruction of pathogens on living tissue.

• Degerming: Mechanical removal of microbes.

• Sanitization: Lowering microbial counts to safe levels.

• Biocide/Germicide: Kills microbes.

• Bacteriostasis: Inhibits growth.

• Asepsis: Absence of contamination.

2. Patterns of Microbial Death

• Microbial death occurs at a constant rate; larger populations take longer to sterilize.

3. Effects of Control Agents

• Agents may damage cell walls, membranes, proteins, or nucleic acids.

• Agents affecting plasma membranes may also affect human cells.

4. Physical Methods of Control

• Moist heat: Boiling, autoclaving, pasteurization.

• Dry heat: Flaming, incineration, hot-air sterilization.

• Filtration: Removes microbes from liquids/gases.

• Low temperature: Inhibits growth.

• High pressure: Denatures proteins.

• Desiccation: Removes water.

• Osmotic pressure: Causes plasmolysis.

• Radiation: Damages DNA (ionizing, nonionizing).

5. Chemical Methods of Control

• Disinfectants: Phenolics, halogens, alcohols, heavy metals, surfactants, aldehydes, peroxygens.

• Halogens: Iodine (antiseptic), chlorine (disinfectant).

• Alcohols: Effective against bacteria, not all viruses.

• Surface-active agents: Soaps, detergents.

• Glutaraldehyde: Effective, kills spores.

• Chemical sterilizers: Ethylene oxide, plasma, peracetic acid.

6. Factors Affecting Disinfection

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

• Gram-negative bacteria are more resistant than gram-positive due to outer membrane.

7. Testing Disinfectants

• Use-dilution test: Tests effectiveness against microbes.

• Disk-diffusion method: Zone of inhibition on agar plate.

Physical Method	Purpose	Example
Moist Heat	Denatures proteins	Autoclaving
Dry Heat	Oxidizes cell components	Hot-air oven
Filtration	Removes microbes	HEPA filters
Radiation	Damages DNA	UV light