Microorganism Cultivation Methods

Cultivation of Microorganisms

• Cultivation is the process of growing organisms by providing suitable environmental conditions.
• Organisms need energy for macromolecule synthesis and maintaining chemical gradients.
• Essential nutrients must be available in a usable form.
• Factors like nutrients, pH, temperature, aeration, salt concentration, and ionic strength must be controlled during growth.
• Metabolic energy generation occurs through fermentation, respiration, and photosynthesis.

Cultivation Methods

• Two key considerations in culturing microorganisms are choosing a suitable medium and isolating bacteria in pure culture.
• Cultivating microorganisms involves raising a crop of cells from a particular species, determining the types and numbers of organisms present in a sample, and isolating a specific organism from a natural source.
• A single cell needs to be isolated and cultivated to ensure all subsequent cells originated from that single cell.

Isolation of Microorganisms in Pure Culture

• Plating Method: Placing a small number of cells on a solidified medium allows each cell to grow into a separate colony.
• Agar is a common solidifying agent extracted from red algae.
• Dilution Method: Reducing the density of microorganisms through serial dilution. The diluted sample is then plated or inoculated, allowing each single cell to grow into a pure colony.
• Samples of each diluted solution are plated or streaked on a solid medium.

Survival of Microorganisms in the Natural Environment

• The number of microorganisms in the biosphere remains relatively constant.
• Survival depends on maintaining a living pool of organisms and successfully competing for necessary nutrients.

The Meaning of Growth

• Growth refers to an increase in the overall components of an organism.
• In unicellular organisms like bacteria, growth involves cell duplication, increasing the population size.

The Growth Curve

• The bacterial growth curve illustrates the population dynamics of bacteria in a closed system.
• Distinct phases in the curve are:
  • Lag phase: Initial adjustment to the new environment, minimal growth.
  • Exponential/log phase: Rapid cell division, constant doubling rate.
  • Stationary phase: Cell division rate equals the death rate, constant population size.
  • Death phase: Number of dying cells exceeds the number of growing cells; population declines.

The Phases of Bacterial Growth

• 1. Lag Phase:* Bacteria adapt to their environment; metabolic activity increases, but little to no cell division occurs.
• 2. Exponential Phase:* Cells divide at a constant rate, creating exponential growth. This phase is highly sensitive to antibiotics and environmental changes. Key processes are DNA replication, protein synthesis, and maximum nutrient utilization.
• 3. Stationary Phase:* Growth rate slows as nutrients are depleted and waste accumulates; new cell production equals cell death, resulting in a stable population.
• 4. Death Phase:* Nutrients become exhausted, waste products accumulate, increasing the death rate of cells. Cells may form spores or enter a dormant state.

Explore the essential aspects of cultivating microorganisms, including the factors that influence their growth and methods to isolate specific organisms. This quiz covers nutrient requirements, environmental conditions, and techniques for achieving pure cultures. Test your understanding of the microbiological principles behind effective cultivation.