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Microbial Nutrition and Growth

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  • Macronutrients in microbial nutrition

    Macronutrients are needed in large amounts and are essential for cell structure and metabolism. Examples include carbon, hydrogen, and oxygen.

  • Micronutrients (Trace Elements) role

    Micronutrients are needed in small amounts and are important for enzyme function and protein structure. Examples include manganese, zinc, and nickel.

  • Difference between inorganic and organic nutrients

    Inorganic nutrients lack both carbon and hydrogen (e.g., water, salts). Organic nutrients contain both carbon and hydrogen, often from living things (e.g., carbohydrates, proteins).

  • Elements comprising 96% of dry microbial cell weight

    Elements CHONPS (carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur) make up 96% of dry cell weight.

  • Definition of heterotroph and autotroph

    Heterotrophs obtain carbon from organic sources. Autotrophs use inorganic CO2 as a carbon source and convert it into organic compounds.

  • Phototroph vs Chemotroph

    Phototrophs use light as an energy source. Chemotrophs use chemical compounds for energy.

  • Role of potassium (K) in microbes

    Potassium is essential for protein synthesis and membrane function.

  • Passive transport mechanisms in microbes

    Passive transport includes diffusion and facilitated diffusion, moving substances from high to low concentration without energy.

  • Active transport in microbial cells

    Active transport requires energy (ATP) and membrane proteins to move substances against the concentration gradient.

  • Osmosis and its effects on microbial cells

    Osmosis is water diffusion through a membrane. In hypotonic solutions, cells swell; in hypertonic, cells shrink (plasmolysis); isotonic solutions cause no net water movement.

  • Temperature classification of microbes: Psychrophiles

    Psychrophiles grow optimally below 15°C and can grow at 0°C.

  • Oxygen requirement: Facultative anaerobes

    Facultative anaerobes use oxygen if present but can grow without it.

  • Microbial association: Mutualism

    Mutualism is a relationship where both organisms benefit.

  • Biofilm formation steps

    Pioneer bacteria colonize a surface, secrete extracellular material, other species join, and biofilms release bacteria to become free-living.

  • Binary fission process in bacteria

    Binary fission involves cell enlargement, chromosome duplication, septum formation, and division into two daughter cells.

  • Phases of bacterial growth curve

    Lag phase (adjustment), exponential phase (rapid growth), stationary phase (birth=death), death phase (cell decline).

  • Methods to measure bacterial growth

    Viable plate count, turbidity measurement, direct microscopic count, Coulter counter, flow cytometer, and genetic probing (PCR).

  • Function of iron (Fe) in microbes

    Iron is essential for cytochrome proteins involved in respiration.

  • Role of magnesium (Mg) in microbial cells

    Magnesium is a component of chlorophyll and stabilizes membranes and ribosomes.

  • Definition of plasmolysis

    Plasmolysis is the shrinking of the cell membrane away from the cell wall due to water loss in hypertonic environments.