Study_Guide___Exam_2

Page 1: Fundamentals of Microbiology Study Guide

• Exam Focus: Chapters 7 & Part of 2, includes lecture notes and microbe minutes.

• Comparison Tables: Create tables to compare features of microbes like:

  • Gram + vs. Gram -

  • Spore former vs. non-spore former

  • Flagellated vs. non-flagellated

  • Pathogenic vs. non-pathogenic

  • Morphology (Cocci, rods, etc.)

1. Required Elements for Growth

• Macronutrients: Required in larger amounts.

  • Carbon: Backbone of organic molecules.

  • Nitrogen: Essential for amino acids and nucleic acids.

  • Phosphorus: Key part of nucleic acids and ATP.

  • Sulfur: Important for amino acids and coenzymes.

  • Oxygen: Forms part of water and organic molecules.

  • Hydrogen: Found in organic compounds and water.

• Micronutrients: Needed in small amounts.

  • Examples: Mn, Zn, Co, Mo, Ni, Cu.

2. Categorizing Organisms

• Energy Sources:

  • Phototrophs: Use light energy (e.g., plants, some bacteria).

  • Chemotrophs: Obtain energy from chemical reactions.

• Carbon Sources:

  • Autotrophs: Fix carbon from inorganic sources (CO₂).

  • Heterotrophs: Acquire carbon from organic compounds.

• Electron Sources:

  • Organotrophs: Source of electrons from organic molecules.

  • Lithotrophs: Source of electrons from inorganic substances.

3. Importance of Nutrients

• Sulfur: Essential for amino acids and coenzymes, critical for protein structure.

• Phosphorus: Vital for nucleic acids, phospholipids, and ATP, essential for cellular processes.

• Nitrogen: Crucial for amino acids, nucleotides; nitrogen fixation converts atmospheric nitrogen into usable forms.

Page 2: Nutritional Factors

4. Growth Factors

• Definition: Organic compounds essential for growth but not synthesized by the organism.

  • Includes amino acids, purines/pyrimidines, and vitamins.

• Importance: Essential for cellular functions and metabolism.

5. Nutrient Concentration and Growth

• Growth rate depends on nutrient availability; the limiting nutrient restricts maximum growth rate.

• Higher concentrations typically increase growth until another factor limits.

6. Role of Oxygen in Growth

• Crucial for aerobic respiration, a highly efficient ATP production method.

  • Obligate aerobes require oxygen.

  • Microaerophiles thrive in reduced oxygen levels.

7. Anaerobes vs. Aerobes

• Aerobes:

  • Obligate aerobes require oxygen.

  • Microaerophiles best in reduced oxygen.

• Anaerobes:

  • Aerotolerant: Not harmed by oxygen.

  • Obligate anaerobes: Cannot grow in oxygen.

  • Facultative: Can use oxygen but grow without it.

8. Reactive Oxygen Species (ROS)

• Definition: Highly reactive molecules containing oxygen.

  • Role in signaling pathways and immune responses.

  • Excessive ROS can cause cellular damage.

• Cleanup Methods:

  • Enzymatic: Converts ROS to less harmful products.

    • Superoxide dismutase, catalase, peroxidases.

  • Non-Enzymatic: Antioxidants (Vitamins C/E, glutathione).

Page 3: Temperature Adaptations

9. Temperature and Microbial Growth

• Microbial Types by Temperature:

  • Psychrophiles: Cold-loving (0°C to 20°C).

  • Mesophiles: Moderate temperature (20°C to 45°C).

  • Thermophiles: Heat-loving (55°C to 85°C).

10. Anaerobic Work Environment Principles

• Purpose: Create oxygen-free spaces for oxygen-sensitive materials.

  • Use anaerobic chambers, GasPak systems, and reducing agents in media.

11. Role of pH and Temperature in Growth

• Optimal pH range varies by microbe:

  • Acidophiles: Low pH.

  • Neutrophiles: Mid pH.

  • Alkalophiles: High pH.

• Optimal temperature affects metabolic rates.

12. Water Availability and Growth

• Osmotic Pressure: Impacts how cells manage water movement.

  • Hypotonic: Water enters, causing swelling.

  • Hypertonic: Water leaves, causing shriveling.

• Water Activity (aw): Amount of water available to organisms affects growth.

13. Adaptations to Extremes

• High Solute Concentrations:

  • Halophiles thrive in high salt.

• High Temperatures:

  • Thermophiles stabilize proteins for optimal growth in heat.

Page 4: Media Types

14. Complex vs. Synthetic Media

• Complex Media: Undefined components, supports varied organisms.

• Synthetic Media: Known quantities of specific chemicals for precise control.

15. Important Complex Media Components

• Peptones: Provide essential amino acids and nitrogen.

• Extracts: Source of vitamins and growth factors for fastidious organisms.

• Agar: Solidifying agent for colony growth.

16. Functional Media Types

• Supportive Media: General-purpose media for many organisms.

• Enriched Media: Nutrient-rich for fastidious organisms.

• Selective Media: Inhibits some microorganisms while promoting others.

• Differential Media: Distinguishes organisms based on biochemical characteristics.

17. Selective vs. Differential Media

• Selective Media: Inhibits some growth (e.g., MacConkey agar).

• Differential Media: Differentiates based on observable changes.

18. Blood Agar vs. MacConkey Agar

• Blood Agar: Enriched medium for fastidious organisms; hemolytic activity.

• MacConkey Agar: Selective for Gram-negative; differentiates lactose fermenters from non-fermenters.

19. Colony Isolation Techniques

• Streak Plate Method: Spreads diluted sample for isolation.

• Spread Plate Method: Distributes microbial sample across the surface.

• Pour Plate Method: Mixes sample with agar to grow colonies both on the surface and within.

Page 5: Counting Microbes & Growth Curve

20. Unculturable Bacteria

• Definition: Cannot be grown using traditional methods.

• Cultivation Methods:

  • DNA amplification, fluorescent probes for visualization.

21. Microbial Consortia

• Groups of microorganisms living together symbiotically.

22. Microbial Counting Techniques

• Direct Counts: Quick estimates without live/dead distinction.

• Viable Cell Counting: Counts living cells as CFUs.

• Turbidity Measurements: Assess cloudiness as an indirect density measure.

23. CFU Calculation

• CFUs represent viable microorganisms; calculated by multiplying colonies by dilution factor.

24. Growth Curve Phases

• Lag Phase: Adaptation to new conditions.

• Exponential Phase: Rapid growth; uniform population.

• Stationary Phase: Growth slows due to limited resources.

• Death Phase: Number of viable cells declines.

25. VBNC & Programmed Cell Death

• Programmed Cell Death: Potential advantages for surviving cells.

• VBNC: Dormant cells alive but not culturable, regrow under favorable conditions.

Page 6: Growth Dynamics

26. Balanced vs. Unbalanced Growth

• Balanced Growth: Constant synthesis rates; optimal conditions.

• Unbalanced Growth: Varies synthesis rates in response to environment changes.

27. Growth Curve Insights

• Generation Time: Time for population to double.

• Growth Rate: Number of generations per unit time.

• Growth Yield: Maximum population or biomass density.

28. Doubling Time Discovery

• Found during Exponential Phase; using Generation Time to determine doubling duration.

29. Importance of Semi-Log Scale

• Transforms exponential growth into a straight line for clarity.

30. Open vs. Closed Systems

• Open System: Continuous nutrient supply; maintains log phase.

• Closed System: No new nutrients added, growth curve observed.

31. Chemostat vs. Turbidostat

• Chemostat: Open system maintaining log phase with limiting nutrients.

• Turbidostat: Regulates flow based on culture turbidity; high dilution rates optimize growth.

32. Sterilization & Disinfection Methods

• Sterilization: Total destruction of viable organisms.

• Disinfection: Kills/Inhibits disease-causing organisms.

• Sanitization: Reduces microbial population to safe levels.

• Antisepsis: Destroys microorganisms on living tissue.

• Chemotherapy: Uses chemicals to inhibit or kill microorganisms in tissues.

Page 7: Efficacy Influences

33. Influencing Factors for Antimicrobial Agents

• Population size, composition, agent concentration, contact time, temperature, local environment.

34. Physical Control Methods

• Filtration: Removes microbes from liquids.

• Heat: Disrupts proteins and nucleic acids.

• Radiation: Uses EM radiation for microbial control.

35. Chemical Control Methods

• Disinfectants: Applied on non-living surfaces.

• Antiseptics: Safe for living tissue.

  • Common Agents: Phenolics, aldehydes, alcohols, halogens, heavy metals, quaternary compounds.

36. Sterilizing Gases

• Used for heat-sensitive items; e.g., ethylene oxide gas.

Page 8: Bacterial Morphology

1. Bacterial Morphology - Size & Shape

• Cocci: Round, can cluster (e.g., staphylococci).

• Bacilli: Rod-like, can form chains.

• Vibrio: Comma-shaped.

• Spirilla: Twisted or spiral.

• Pleiomorphic: Variable shapes depending on environment.

2. Surface/Volume Ratio (S/V)

• Higher S/V ratio improves nutrient absorption & waste removal efficiency.

3. Bacterial Cell Structure

• Cytoplasm: Contains nucleoid, plasmids, ribosomes, inclusion bodies.

  • Nucleoid: Site of chromosomal DNA.

  • Plasmids: Independent small DNA circles providing advantages.

  • Ribosomes: Protein synthesis sites (30S and 50S subunits).

Page 9: Cell Structure

• Inclusion Bodies: Energy storage & buoyancy (e.g., gas vesicles).

• Cytoskeleton: Internal proteins for structure and organization (e.g., FtzS, MreB).

4. Plasma Membrane

• Composed of a phospholipid bilayer regulating entry/exit.

  • Membrane Proteins: Peripheral and integral proteins for functions like transport.

  • Dynamic Nature: Lipids composition changes with conditions.

Page 10: Material Movement

5. Material Movement Into Cells

• Passive Diffusion: Moves molecules without energy (high to low concentration).

• Facilitated Diffusion: Specific carrier proteins aid in movement without energy.

• Active Transport: Energy required to move against concentration gradients.

  • Primary: Directly uses ATP.

  • Secondary: Uses gradients from primary.

  • Group Translocation: Modifies molecules during transport (PTS system).

6. Material Movement Out of Cells

• Sec System: General secretion pathway for proteins across membranes.

Page 11: Cell Wall Composition

6. Cell Wall Structre & Function

• Peptidoglycan: Composed of NAG and NAM; structural integrity.

  • Gram-positive: Thick peptidoglycan, retains crystal violet.

  • Gram-negative: Thinner peptidoglycan, outer membrane.

7. Antibiotic Mechanisms

• Lysozyme: Disrupts peptidoglycan structure.

• Lysostaphin: Targets specific Staphylococci structures.

• Beta-Lactam Antibiotics: Inhibit cell wall synthesis by affecting PBPs.

Page 12: Peptidoglycan Structure

8. Peptidoglycan Characteristics

• Composed of alternating NAG and NAM linked by peptide chains for structural strength.

9. Antibiotic Actions

• Vancomycin: Inhibits cell wall synthesis by binding to precursors.

• Amoxicillin & Penicillin: Inhibit synthesis by blocking PBPs.

Page 13: Microbe Minutes - Characteristics

1. Enterococcus faecalis

• Characteristics: Spherical, forms chains; found in gut, non-motile, facultative anaerobe;

• Pathogenicity: Opportunistic; causes endocarditis, sepsis, UTIs.

2. Vibrio vulnificus

• Shape: Curved rod, requires salt; pathogenic, causes vibriosis.

• Transmission: Through contaminated seafood; high mortality in compromised.

3. Deinococcus radiodurans

• Known for: Extreme radiation resistance and desiccation; "world's toughest bacterium".

4. Treponema pallidum

• Characteristic: Spiral-shaped, obligate intracellular pathogen; causes syphilis.

5. Neisseria meningitidis

• Shape: Cocci/diplococci; can cause meningitis, transmitted by droplets.

Page 14: Overview of Archaea

1. Domains of Life

• Three Domains: Eukaryota, Eubacteria, Archaebacteria (now Archaea).

2. Methanogens

• Characteristics: Methane-producing, thrive in anaerobic conditions.

3. Importance of Methane

• Environmental Impact: Greenhouse gas, potential biofuel.

Page 15: Methanogenesis

1. Unique Metabolic Pathways

• Only archaea produce methane via methanogenesis.

2. Carbonic Anhydrase Role

• Enzyme pivotal for carbon dioxide to bicarbonate conversion.

Page 16: Conclusion and Future Directions

1. Research Statement

• Evaluating methanogenic archaea's role in ecosystems and health implications.

2. Future Directions

• Continued research on methanogens’ role in climate change and biofuel production.