Microbial Nutrition and Oxygen Requirements

Microbial nutritional needs:
- Macronutrients: Carbon, nitrogen, phosphorus, sulfur
- Micronutrients: Potassium, sodium, chlorine, magnesium, calcium, iron, zinc, molybdenum
- Organic Growth Factors: Vitamins and co-enzymes (e.g., Niacin for NAD+)

Obligate aerobes: Require oxygen for respiration.
Facultative anaerobes: Can use oxygen for respiration if available, but can also use anaerobic pathways (fermentation, anaerobic respiration).
Microaerophiles: Require low oxygen concentrations for respiration.
Obligate anaerobes: Cannot use oxygen for respiration, find it toxic.
Aerotolerant anaerobes: Do not use oxygen but can survive in its presence.

Reactive Oxygen Species (ROS): Superoxide (O2-) is highly reactive and can damage DNA, proteins, and other cell components.
Enzymes that detoxify ROS:
- Superoxide dismutase (SOD): Converts superoxide to hydrogen peroxide (H2O2).
- Catalase: Converts hydrogen peroxide to water (H2O) and oxygen (O2).

Temperature:
- Psychrophiles: Grow best at low temperatures (4°C).
- Mesophiles: Grow best at moderate temperatures (20-45°C).
- Thermophiles: Grow best at high temperatures (50-80°C).
- Hyperthermophiles: Grow best at extremely high temperatures (80°C+).
pH:
- Acidophiles: Grow best at acidic pH (below 5.5).
- Neutrophiles: Grow best at neutral pH (6.5-7.5).
- Alkalophiles: Grow best at alkaline pH (above 8.5).
Osmotic Pressure: Refers to the concentration of solutes outside the cell compared to inside.
- Isotonic: Equal solute concentrations inside and outside the cell.
- Hypotonic: Lower solute concentration outside the cell than inside.
- Hypertonic: Higher solute concentration outside the cell than inside.
- Plasmolysis: Occurs in hypertonic environments, causing cell shrinkage due to water loss.
- Halophiles: Thrive in high salt concentrations.

Growth: Refers to an increase in the number of cells, not an increase in cell size.
Binary Fission: Most bacteria reproduce through this process, where one cell divides into two identical daughter cells.

Sterilization: Killing or removal of all microorganisms.
Disinfection: Killing or inhibiting the growth of pathogens on inanimate objects.
Antisepsis: Killing or inhibiting the growth of pathogens on living tissue.
Bacteriostatic: Inhibiting the growth of bacteria without killing them.
Bactericidal: Killing bacteria.

Time and temperature: Higher temperatures and longer exposure times generally increase effectiveness.
Type and number of microbes: Some microbes are more resistant to control methods than others.
Physiological state of microbes: Metabolically active cells are more susceptible to control methods.
Environment: Some chemical agents are deactivated by the presence of organic compounds (blood, pus, fecal waste, etc.).

Heat:
- Dry Heat: Incineration (flaming) and oven heating (sterilizing).
- Moist Heat:
  - Boiling: Effective for killing most vegetative bacteria, but not spores.
  - Autoclave: Uses high pressure steam to sterilize materials.
  - Pasteurization: Uses controlled heating to reduce the number of pathogens in food.
Filtration: Physically removes microbes by passing a liquid or gas through a filter with pore sizes small enough to trap microorganisms.
Low Temperatures:
- Refrigeration: Slows but does not stop microbial growth (bacteriostatic).
- Freezing: Can also be bacteriostatic.
- Lyophilization (freeze-drying): Preserves microorganisms by freezing them and removing water under a vacuum.
Osmotic Pressure: Using salts or sugars to create a hypertonic environment, causing plasmolysis and inhibiting microbial growth.
Radiation:
- Ionizing Radiation: High-energy radiation (X-rays, gamma rays) that damages DNA and proteins.
- Non-ionizing Radiation: Lower-energy radiation (UV light) that damages DNA.

Soaps and Detergents: Surfactants that disrupt cell membranes.
- Quaternary ammonium compounds (Quats): Effective surface disinfectants.
Phenol and Derivatives: Damage membranes and denature proteins.
- Lysol, Chlorhexidine: Examples of phenol derivatives.
Alcohols: Denature proteins and damage membranes.
- Ethanol, Isopropanol: Common alcohols used as disinfectants.
Halogens: Damage proteins.
- Chlorine: Used to sanitize water, active ingredient in bleach.
- Iodine: Effective antiseptic.
Heavy Metals: Damage proteins.
- Silver nitrate: Used in eye drops for newborns to prevent infection.
- Organic mercury: Used as an antiseptic.
Organic Acids: Bacteriostatic by slowing or preventing fermentation.
- Sorbic acid, Benzoic acid: Common food preservatives.
Oxidizing Agents: Break disulfide bridges in proteins.
- Hydrogen peroxide: Antiseptic, used for cleaning wounds.