Microbial Nutrition and Growth - Chapter 9

Overview

• Microbes require nutrients and a source of energy for growth, similar to other living organisms.
• Nutrients are acquired from the environment and are essential for cellular activities like growth and division.

Nutrients and Elements

• Essential elements for all organisms: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur.
• Macronutrients: Needed in large amounts (e.g., C, H, O, N, P, S).
• Micronutrients (Trace Elements): Needed in smaller amounts (e.g., Copper, Zinc, Iron).
  • Often function as co-factors in enzymes.
• Inorganic Nutrients: Lack carbon (e.g., Iron, Zinc, Sulfur).
• Organic Nutrients: Contain carbon and hydrogen (e.g., Vitamins, Growth factors).

Nutritional Types

• Heterotrophs: Obtain carbon from organic compounds.
• Autotrophs: Obtain carbon from CO2.
• Phototrophs: Capture energy from sunlight.
• Chemotrophs: Obtain energy from chemical compounds.

Unique Nutritional Types

• Photoautotrophs: Energy from sunlight, carbon from CO2 (e.g., Plants, Algae).
• Chemoheterotrophs: Energy and carbon from organic molecules.
• Chemoautotrophs: Energy from inorganic molecules, carbon from CO2.

Nutrient Transport

• Diffusion: Movement from high to low concentration (spontaneous, no energy required).
• Osmosis: Diffusion of water across a membrane.
• Active Transport: Movement against a concentration gradient (requires energy).
• Bulk Transport: Includes endocytosis (phagocytosis for solids, pinocytosis for liquids).

Environmental Factors Influencing Growth

• Temperature: Each organism has a minimum, maximum, and optimum temperature for growth.
  • Groups: Psychrophiles, Psychrotolerant, Mesophiles, Thermophiles, Extreme Thermophiles.
• Oxygen: Different microbes have varied oxygen requirements.
  • Aerobes (use oxygen), Anaerobes (do not use oxygen), Facultative Anaerobes (can use oxygen but don't need it), Microaerophiles, Aerotolerant Anaerobes.
• pH: Organisms can be acidophiles (acidic environments) or alkaliphiles (basic environments).
• Osmotic Pressure: Osmophiles thrive in high solute concentrations; Halophiles specifically prefer high salt concentrations.

Symbiotic Relationships

• Mutualism: Both organisms benefit.
• Commensalism: One benefits, the other is neither harmed nor helped.
• Parasitism: Parasite benefits at the host's expense.

Biofilms

• Complex communities of microbes that attach to surfaces, often secured by extracellular materials.
• Quorum Sensing: Process allowing bacteria to coordinate behavior based on population density.

Bacterial Growth

• Binary Fission: Simple process of cell division in bacteria.
• Growth Curve Phases:
  • Lag Phase: No immediate increase in cell number.
  • Exponential (Log) Phase: Rapid cell division and population increase.
  • Stationary Phase: Growth rate slows as nutrients deplete.
  • Death Phase: Nutrient exhaustion and waste accumulation lead to cell death.

Practical Implications

• Understanding microbial growth is crucial for food preservation (e.g., refrigeration, salting, pickling).
• Microbial characteristics aid in medical and environmental applications.