BMSC 210 - Microbiology Notes

Microbial Growth Overview

Metabolism

• Metabolism Definition: Sum of all biochemical reactions in an organism.
  • Catabolism: Breakdown of complex molecules to release energy.
  • Anabolism: Synthesis of cellular components from simpler molecules.

Gibbs Free Energy

• Chemical Reactions and Energy: Involves changes in Gibbs Free Energy ().
  • Exergonic Reaction:  AG < 0 (spontaneous, releases energy)
  • Endergonic Reaction:  AG > 0 (not spontaneous, requires energy input)

Metabolic Classes of Microorganisms

• Phototroph: Obtains energy from light.
• Chemotroph: Obtains energy from chemical compounds.
• Lithotroph: Inorganic electron donors.
• Organotroph: Organic electron donors.
• Heterotroph: Uses organic compounds as carbon sources.
• Autotroph: Uses CO2 as carbon source.

Electron Transport in Microbes

• Electron Transportation: Microbes utilize different electron donors and acceptors to generate energy.
  • Better Electron Donors: e.g., NADH, FADH2
  • Better Electron Acceptors: e.g., O2, NO3-

Enzymatic Activity

• Function of Enzymes: Lower activation energy for reactions.
  • Steps in Enzymatic Reactions:
  1. Substrate binds to enzyme's active site.
  2. Enzyme-substrate complex forms.
  3. Substrate is converted to products.
  4. Products are released.

Carbohydrate Catabolism

• Stages of Breakdown:
  • Glycolysis: Conversion of glucose to pyruvate.
  • Produces ATP and NADH.
  • Krebs Cycle: Processes acetyl-CoA to generate energy carriers (NADH, FADH2) and ATP.

Microbial Respiration

• Types of Respiration:
  • Aerobic Respiration: Uses O2 as terminal electron acceptor, yielding maximum ATP.
  • Anaerobic Respiration: Uses other molecules (e.g., nitrate, sulfate) as terminal electron acceptors, yielding less ATP than aerobic.

Fermentation

• Process: Breakdown of organic substances without oxygen.
• End Products: Produce organic acids, alcohols, and CO2.
• Types:
  • Homofermentation: Produces one fermentation product.
  • Heterofermentation: Produces multiple products.

Growth and Reproduction in Bacteria

• Binary Fission: Process by which bacteria divide, leading to two daughter cells.
• Bacterial Cell Cycle Stages:
  1. Chromosome replication
  2. Cell elongation
  3. Segregation
  4. Z-ring formation
  5. Division

Quantifying Growth

• Direct Methods: Counting cells using microscopy or Coulter counter.
• Viable Counts: Through dilution plating, calculating colony-forming units (CFUs).

Factors Affecting Growth

• Nutrient Requirements: Essential nutrients include carbon, nitrogen, and electron donors and acceptors.
  • Auxotrophs: Need additional nutrients that they can't produce.
• Media Types:
  • Defined vs. Complex; Minimal, Selective, and Differential media.

Environmental Factors

• Oxygen Requirement:
  • Obligate aerobes, anaerobes, facultative anaerobes, and microaerophiles.
• Temperature, pH, and Salt: Various types of microbes classified based on their preferences for temperature, pH levels, and salinity conditions.

Additional Notes

• Upcoming Modules: Prepare for next classes on genetics, transcription, and translation as per readings in specified chapters.
• Poll Everywhere: Look out for interactive questions to assess understanding during lectures.