Continuous Culture Systems Overview
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Questions and Answers

What is one disadvantage of using counting chambers for counting microorganisms?

  • They are expensive to use.
  • Only a small volume of the population is sampled. (correct)
  • They do not provide information about microbial morphology.
  • They are not useful for small populations.

    • How does flow cytometry enhance the counting of microorganisms?

  • By using a microscope to visually inspect each cell.
  • By separating cells in space to detect light scattering events individually. (correct)
  • By requiring a larger sample size than traditional methods.
  • By relying solely on the size of the cells for counting.

    • In a Coulter counter, what physical change is measured to count microbial cells?

  • Sound waves generated by the cells.
  • Optical density changes of the microbial suspension.
  • Changes in electrical resistance as cells pass through a small hole. (correct)
  • Temperature increase as cells pass through the counter.

    • What additional information can flow cytometry provide apart from cell counting?

    <p>Detailed characteristics about the population of cells.</p> Signup and view all the answers

    Why might traditional direct counting methods yield higher cell densities than plating methods?

    <p>They do not differentiate between living and dead cells.</p> Signup and view all the answers

    What characteristic of the counting chamber is essential for its usage?

    <p>A specially etched grid at the bottom.</p> Signup and view all the answers

    Which method uses laser light to count microbial cells as they pass through a beam?

    <p>Flow cytometry.</p> Signup and view all the answers

    What type of sample preparation is often necessary for using advanced flow cytometry techniques?

    <p>Fluorescent dyes or fluorescently labeled antibodies.</p> Signup and view all the answers

    What determines the growth rate in a chemostat?

    <p>The rate at which sterile medium is fed into the growth chamber</p> Signup and view all the answers

    What is the relationship between microbial cell biomass and light scattering in spectrophotometry?

    <p>Light scattering is directly proportional to cell biomass.</p> Signup and view all the answers

    Which characteristic distinguishes turbidostats from chemostats?

    <p>Nutrient levels in turbidostats are always in excess</p> Signup and view all the answers

    At what absorbance level is a dilution of the sample necessary for accurate measurement in spectrophotometry?

    <p>0.5</p> Signup and view all the answers

    What is indicated by the dilution rate (D) in a chemostat?

    <p>The flow rate of sterile medium into the vessel relative to its volume</p> Signup and view all the answers

    What forms the primary source of energy for cellular processes in living organisms?

    <p>Adenosine triphosphate (ATP)</p> Signup and view all the answers

    What is the primary purpose of using a Petroff-Hausser counting chamber?

    <p>To directly count microbial numbers</p> Signup and view all the answers

    Which statement best describes the role of nutrients in microbial growth?

    <p>Nutrients are essential for both biosynthesis and energy production.</p> Signup and view all the answers

    In a turbidostat, how does the flow rate of media change?

    <p>It varies to maintain a desired turbidity</p> Signup and view all the answers

    What must microbial cells achieve to support growth and metabolism?

    <p>Polymerize building blocks into various macromolecules.</p> Signup and view all the answers

    Which statement is true regarding the nutrient requirements in chemostats and turbidostats?

    <p>Nutrient levels in turbidostats are not limiting</p> Signup and view all the answers

    In which context is ATP described as the 'energy currency' of the cell?

    <p>Cells earn ATP through certain processes and spend it on others.</p> Signup and view all the answers

    What is the relationship between turbidity and cell density in a turbidostat?

    <p>Increasing turbidity correlates with increasing cell density</p> Signup and view all the answers

    Which of the following accurately represents a requirement for microbial biosynthesis?

    <p>Building blocks must be synthesized or preformed.</p> Signup and view all the answers

    What is the effect of dilution rate on stability in chemostats?

    <p>Lower dilution rates are most stable and effective</p> Signup and view all the answers

    What occurs when the cell concentration exceeds an absorbance level of 0.5 in spectrophotometry?

    <p>The sample needs to be diluted for accurate readings.</p> Signup and view all the answers

    What are the three major classes of growth factors?

    <p>Amino acids, purines and pyrimidines, vitamins</p> Signup and view all the answers

    What role do vitamins play in microbial growth?

    <p>They are essential for enzyme cofactor functions in small amounts.</p> Signup and view all the answers

    How is energy primarily stored in bacterial cells?

    <p>As high-energy-transfer compounds like ATP</p> Signup and view all the answers

    What drives the flagellar motor in bacterial cells?

    <p>Proton motive force from the electric potential and hydrogen gradient</p> Signup and view all the answers

    Which of the following is NOT a function of ATP in bacteria?

    <p>Storage of genetic information</p> Signup and view all the answers

    What distinguishes bacterial flagella from those of eukaryotic microorganisms?

    <p>Bacterial flagella can rotate without ATP.</p> Signup and view all the answers

    What is the result of the inward flux of protons in bacterial cells?

    <p>Flagellar rotation</p> Signup and view all the answers

    What process is involved in the active transport of nutrients across the cytoplasmic membrane?

    <p>Utilization of membrane carrier proteins</p> Signup and view all the answers

    Which type of energy is used to drive endergonic reactions required for bacteria?

    <p>Energy from ATP and proton motive force</p> Signup and view all the answers

    What is a primary function of the electrochemical proton gradient in bacterial cells?

    <p>Driving the flagellar motor and ATP synthesis</p> Signup and view all the answers

    What role do uridine diphosphate (UDP) derivatives play in peptidoglycan synthesis?

    <p>They act as carriers for NAG-NAM-pentapeptide units.</p> Signup and view all the answers

    Which of the following antibiotics inhibits the transpeptidation reaction in peptidoglycan synthesis?

    <p>Penicillin</p> Signup and view all the answers

    Which of the following best describes the primary source of carbon for chemoautotrophic bacteria?

    <p>CO2</p> Signup and view all the answers

    What is the main function of ribulose-1,5-bisphosphate carboxylase in the Calvin cycle?

    <p>To fix CO2 to RuBP</p> Signup and view all the answers

    During the reduction phase of the Calvin cycle, what is reduced to form glyceraldehyde 3-phosphate?

    <p>3-phosphoglycerate (PGA)</p> Signup and view all the answers

    What is the primary result of the Calvin cycle in terms of metabolic products?

    <p>Glucose and other carbohydrates</p> Signup and view all the answers

    What does the formation of cross-links in peptidoglycan synthesis involve?

    <p>Transpeptidation</p> Signup and view all the answers

    In the regeneration phase of the Calvin cycle, what molecules are primarily produced?

    <p>Fructose and glucose</p> Signup and view all the answers

    What type of reactions does metabolism encompass within a living organism?

    <p>All chemical reactions</p> Signup and view all the answers

    How does penicillin disrupt bacterial cell walls?

    <p>By preventing transpeptidation</p> Signup and view all the answers

    Study Notes

    Continuous Culture Systems

    • Chemostat:

      • Operates with a constant rate of sterile medium inflow and microorganism outflow.
      • Limited essential nutrient determines the growth rate and final cell density.
      • Dilution rate (D) calculated as D = f/V, where f is flow rate and V is vessel volume.

    • Turbidostat:

      • Utilizes a photocell to monitor culture turbidity, automating flow rate to maintain a set cell density.
      • Contains excess nutrients; operates best at high dilution rates.
      • Differs from chemostat in that its dilution rate varies rather than remaining constant.

    Measuring Microbial Growth

    • Direct Measurement Techniques:

      • Petroff-Hausser Counting Chamber: Enables direct counts of microbes, providing information on size and shape; relies on even population distribution.
      • Flow Cytometry: Counts cells by measuring light scattering as cells pass through a laser; can provide detailed cellular information using fluorescent markers.
      • Coulter Counter: Counts microbes based on electrical resistance changes as cells traverse a small aperture; may include dead cells in counts.

    • Spectrophotometry:

      • Measures turbidity in relation to cell mass; absorbance correlates to cell concentration, effective for high-density populations.

    Microbial Metabolism

    • Nutritional Requirements:

      • Three key growth factors: amino acids (for proteins), purines/pyrimidines (for nucleic acids), vitamins (coenzymes for enzymatic reactions).
      • Nutrients are crucial for biosynthesis and energy production.

    • Energy Utilization:

      • ATP serves as the primary energy currency, generated via metabolic processes.
      • Energy aids in cellular functions, including biosynthesis and maintaining ion gradients.

    Bacterial Motility

    • Flagellar Activity:
      • Bacterial flagella do not derive energy from ATP; instead, they utilize the proton motive force generated across the cytoplasmic membrane.
      • Proton influx drives the flagellar motor, a mechanism distinct from other eukaryotic cilia and flagella.

    Nutritional Uptake and Synthesis

    • Transport Mechanisms:

      • Nutrients cross membranes via passive diffusion or through membrane carrier proteins, ensuring selective nutrient uptake.
      • Peptidoglycan synthesis involves UDP derivatives and bactoprenol, emphasizing the complexity of bacterial cell wall formation.

    • Antimicrobial Vulnerability:

      • Peptidoglycan synthesis is a primary target for antibiotics; disruptions can lead to cell lysis.

    Chemoautotrophic Bacteria and the Calvin Cycle

    • CO2 Fixation:

      • Chemoautotrophic bacteria convert inorganic nutrients into metabolic energy and organic cell material using the Calvin Cycle.
      • Key enzyme: ribulose bisphosphate carboxylase (rubisco), essential for CO2 fixation.

    • Phases of the Calvin Cycle:

      • Carboxylation: RuBP combines with CO2 to produce PGA.
      • Reduction: PGA is converted to glyceraldehyde 3-phosphate using NADP; partially reverses glycolysis.
      • Regeneration: RuBP is regenerated, producing carbohydrates like glucose; defined by high ATP and NADPH usage.

    Overview of Metabolic Processes

    • Metabolism: Encompasses all cellular chemical reactions; includes aerobic respiration (glycolysis, TCA cycle, electron transport chain) and anaerobic processes like fermentation.

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    Description

    Explore the two major types of continuous culture systems: chemostats and turbidostats. This quiz will cover the construction and function of chemostats, where nutrient limitation plays a crucial role in microbial growth rates. Test your understanding of these essential concepts in microbiology!

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