Microbial Nutrition Basics

Microbial Nutrition

• Nutrition involves the uptake of nutrients from the environment for metabolism and growth.
• Essential nutrients are required because organisms cannot synthesize them.
• Macronutrients (C, H, O, N, K, P, S) are needed in large quantities to form macromolecules (nucleic acids, proteins, carbohydrates, lipids).
• Micronutrients (trace elements like Zn, Mn) are crucial in smaller amounts for enzyme activity and protein structure.

Sources of Essential Nutrients

• Essential nutrients originate from inorganic reservoirs (rocks, atmosphere, oceans), and many organisms acquire nutrients from others that have already incorporated them.
• Carbon sources vary:
  • Heterotrophs require organic carbon sources (e.g., glucose).
  • Autotrophs utilize inorganic carbon (CO2), functioning as self-feeders.
• Nitrogen sources include nitrogen fixation (converting N2 gas to NH3) and the breakdown of molecular compounds (DNA, RNA, ATP).
• Oxygen sources come from the atmosphere (20% O2), organic compounds, and inorganic salts (phosphates, nitrates, sulfates).
• Hydrogen sources are environmental gases such as H2S, CH4, and H2.
• Phosphorus is obtained through weathering of rocks and sediment as phosphate.
• Sulfur also derives from weathering geological formations.
• Other important nutrients in microbial metabolism include K, Na, Ca, Fe, Mg, and Zn.
• Growth factors are vital organic compounds (amino acids, vitamins, nitrogenous bases) that cannot be synthesized and must be ingested.

Nutritional Types of Microbes

• Nutritional types are determined by the carbon and energy sources utilized.
• Phototrophs derive energy from photosynthesis (not covered in this course).
• Chemotrophs obtain energy from chemical compounds:
  • Chemoheterotrophs utilize organic compounds for both carbon and energy (e.g., aerobic respiration).
  • Saprobic microorganisms feed on dead organic matter:
    • Obligate saprobes cannot live in a host and thrive in free-living conditions.
    • Facultative parasites infect a host when the immune system allows (opportunistic pathogens).
  • Parasitic microorganisms depend entirely on hosts:
    • Pathogens can cause disease or death.
    • Obligate parasites cannot survive without a host (e.g., syphilis bacterium).
    • Obligate intracellular parasites require host cells for part or all of their lifecycle (e.g., viruses).

Transport Mechanisms for Nutrient Absorption

• Organisms utilize multiple mechanisms to move nutrients in and waste out:
  • Diffusion: Movement of substances from high concentration to low until equilibrium is reached; effective for small, non-polar molecules (O2, CO2).
  • Osmosis: Movement of water through a selectively permeable membrane from areas of high water concentration to low.
    • Cell walls allow large water movement, and small water molecules can pass through plasma membranes.
    • Selectively permeable membranes permit movement based on size and charge.
    • Tonicity influences water movement:
      • Hypotonic: Solute concentration outside the cell is lower, resulting in water influx.
      • Hypertonic: Solute concentration outside is higher, leading to water movement out of the cell.
      • Isotonic: Equal solute concentrations outside and inside, resulting in no net water movement.

Explore the essential concepts of microbial nutrition, focusing on the uptake of macronutrients and micronutrients necessary for growth and metabolism. Learn about the various sources of these nutrients and the roles of heterotrophs and autotrophs in acquiring them. This quiz is designed to enhance your understanding of how microbes interact with their environment for nutritional needs.