Unit Two: Microbial Growth - Lecture Notes

Chapters 6-8 Overview

Focus: Microbial growth, functions, energy production, food sourcing
Elements required by all living things: Carbon, Hydrogen, Oxygen, Phosphorus, Nitrogen
Varying sources and amounts of these elements

Microbes require various essential nutrients from their environment
- Macronutrients: Needed in large amounts (C, H, O)
- Micronutrients (trace elements): Needed in small amounts (Zinc, Nickel)
Organic vs Inorganic Nutrients: Carbon Content
- Organic: Contain carbon (carbs, lipids, proteins)
- Inorganic: No carbon (water, gases, metals)

Carbon: Brought in through organic molecules (carbs, lipids, proteins, nucleic acids)
Hydrogen: Maintains pH, forms bonds, energy source in respiration (water, salts)
Sulfur: Needed for vitamins, amino acids (rocks, mineral sediments)
Nitrogen: Builds proteins and nucleic acids (nitrogen gas)
Phosphorus: Makes nucleic acids, enzymes, membranes (phosphoric acid, mineral deposits)
Oxygen: Required for structural and enzymatic functions (organic/inorganic compounds)
Other Nutrients: Potassium, Sodium, Calcium, Magnesium, Iron, Zinc, etc.

Carbon and Energy Sources
- Autotrophs: Use CO2 for carbon
  - Photoautotrophs: Use sunlight for energy
  - Chemoautotrophs: Use chemical compounds for energy
- Heterotrophs: Obtain carbon from organic sources
  - Photoheterotrophs: Use sunlight
  - Chemoheterotrophs: Use chemical compounds
  - Saprobes: Decomposers, free-living
  - Parasites: Derive nutrients from living host

Diffusion and Osmosis
- Diffusion: Movement from high to low concentration
- Osmosis: Diffusion of water
  - Types of Osmotic Environments: Hypertonic, isotonic, hypotonic
Transport Processes
- Passive Transport: No energy required, moves from high to low concentration
  - Simple Diffusion: Directly through membrane
  - Facilitated Diffusion: Through channels or pores
- Active Transport: Requires energy, moves from low to high concentration
- Exocytosis vs. Endocytosis: Movement out of/into the cell
  - Phagocytosis: Bringing in large matter
  - Pinocytosis: Bringing in liquids

Temperature Ranges
- Psychrophiles: 0-15°C (cold-loving)
- Psychrotrophs: 15-30°C (cold-tolerant)
- Mesophiles: 10-50°C (moderate temperatures)
- Thermophiles: 45-80°C (heat-loving)
- Hyperthermophiles: 80-120°C (extreme heat)
Gas Requirements
- Oxygen: Vital for aerobic respiration
  - Aerobes (need oxygen), Facultative Anaerobes (prefer oxygen), Anaerobes (killed by oxygen), Aerotolerant Anaerobes (don't use oxygen but tolerate it), Microaerophiles (need low oxygen)
- Carbon Dioxide: Required for metabolism
  - Capnophiles: Grow best at high CO2 levels
pH Preferences
- Neutrophils: Prefer neutral (pH 6-8)
- Acidophiles: Prefer acidic (lower pH)
- Alkalinophiles: Prefer basic or alkaline (higher pH)
Osmotic Pressure
- Isotonic: Preferred by most organisms
- Osmophiles: Prefer hypertonic environments (high salt concentration)
  - Halophiles: Salt lovers
Radiation and Pressure
- Barophiles: Thrive under high pressure (deep ocean)
Symbiotic Relationships
- Mutualism: Both benefit
- Commensalism: One benefits, the other unaffected
- Parasitism: One benefits, the other is harmed

Binary Fission: Main form of microbial reproduction
- Generation Time: Time for one cycle (can vary from minutes to months)
- Exponential Growth: Doubling each generation, represented by 2^n

Growth Curve Phases:
- Lag Phase: No new bacteria, acclimation
- Log Phase: Rapid, exponential growth
- Stationary Phase: Growth stabilizes (nutrient/space competition)
- Death Phase: Decline in population due to resource depletion
Methods of Population Measurement:
- Turbidity: Cloudiness indicates growth
- Direct Counting: Mechanical or automated methods
- Genetic Probing: PCR techniques for counting without cultivation