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Questions and Answers
What is one disadvantage of using counting chambers for counting microorganisms?
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?
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?
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?
What additional information can flow cytometry provide apart from cell counting?
Why might traditional direct counting methods yield higher cell densities than plating methods?
Why might traditional direct counting methods yield higher cell densities than plating methods?
What characteristic of the counting chamber is essential for its usage?
What characteristic of the counting chamber is essential for its usage?
Which method uses laser light to count microbial cells as they pass through a beam?
Which method uses laser light to count microbial cells as they pass through a beam?
What type of sample preparation is often necessary for using advanced flow cytometry techniques?
What type of sample preparation is often necessary for using advanced flow cytometry techniques?
What determines the growth rate in a chemostat?
What determines the growth rate in a chemostat?
What is the relationship between microbial cell biomass and light scattering in spectrophotometry?
What is the relationship between microbial cell biomass and light scattering in spectrophotometry?
Which characteristic distinguishes turbidostats from chemostats?
Which characteristic distinguishes turbidostats from chemostats?
At what absorbance level is a dilution of the sample necessary for accurate measurement in spectrophotometry?
At what absorbance level is a dilution of the sample necessary for accurate measurement in spectrophotometry?
What is indicated by the dilution rate (D) in a chemostat?
What is indicated by the dilution rate (D) in a chemostat?
What forms the primary source of energy for cellular processes in living organisms?
What forms the primary source of energy for cellular processes in living organisms?
What is the primary purpose of using a Petroff-Hausser counting chamber?
What is the primary purpose of using a Petroff-Hausser counting chamber?
Which statement best describes the role of nutrients in microbial growth?
Which statement best describes the role of nutrients in microbial growth?
In a turbidostat, how does the flow rate of media change?
In a turbidostat, how does the flow rate of media change?
What must microbial cells achieve to support growth and metabolism?
What must microbial cells achieve to support growth and metabolism?
Which statement is true regarding the nutrient requirements in chemostats and turbidostats?
Which statement is true regarding the nutrient requirements in chemostats and turbidostats?
In which context is ATP described as the 'energy currency' of the cell?
In which context is ATP described as the 'energy currency' of the cell?
What is the relationship between turbidity and cell density in a turbidostat?
What is the relationship between turbidity and cell density in a turbidostat?
Which of the following accurately represents a requirement for microbial biosynthesis?
Which of the following accurately represents a requirement for microbial biosynthesis?
What is the effect of dilution rate on stability in chemostats?
What is the effect of dilution rate on stability in chemostats?
What occurs when the cell concentration exceeds an absorbance level of 0.5 in spectrophotometry?
What occurs when the cell concentration exceeds an absorbance level of 0.5 in spectrophotometry?
What are the three major classes of growth factors?
What are the three major classes of growth factors?
What role do vitamins play in microbial growth?
What role do vitamins play in microbial growth?
How is energy primarily stored in bacterial cells?
How is energy primarily stored in bacterial cells?
What drives the flagellar motor in bacterial cells?
What drives the flagellar motor in bacterial cells?
Which of the following is NOT a function of ATP in bacteria?
Which of the following is NOT a function of ATP in bacteria?
What distinguishes bacterial flagella from those of eukaryotic microorganisms?
What distinguishes bacterial flagella from those of eukaryotic microorganisms?
What is the result of the inward flux of protons in bacterial cells?
What is the result of the inward flux of protons in bacterial cells?
What process is involved in the active transport of nutrients across the cytoplasmic membrane?
What process is involved in the active transport of nutrients across the cytoplasmic membrane?
Which type of energy is used to drive endergonic reactions required for bacteria?
Which type of energy is used to drive endergonic reactions required for bacteria?
What is a primary function of the electrochemical proton gradient in bacterial cells?
What is a primary function of the electrochemical proton gradient in bacterial cells?
What role do uridine diphosphate (UDP) derivatives play in peptidoglycan synthesis?
What role do uridine diphosphate (UDP) derivatives play in peptidoglycan synthesis?
Which of the following antibiotics inhibits the transpeptidation reaction in peptidoglycan synthesis?
Which of the following antibiotics inhibits the transpeptidation reaction in peptidoglycan synthesis?
Which of the following best describes the primary source of carbon for chemoautotrophic bacteria?
Which of the following best describes the primary source of carbon for chemoautotrophic bacteria?
What is the main function of ribulose-1,5-bisphosphate carboxylase in the Calvin cycle?
What is the main function of ribulose-1,5-bisphosphate carboxylase in the Calvin cycle?
During the reduction phase of the Calvin cycle, what is reduced to form glyceraldehyde 3-phosphate?
During the reduction phase of the Calvin cycle, what is reduced to form glyceraldehyde 3-phosphate?
What is the primary result of the Calvin cycle in terms of metabolic products?
What is the primary result of the Calvin cycle in terms of metabolic products?
What does the formation of cross-links in peptidoglycan synthesis involve?
What does the formation of cross-links in peptidoglycan synthesis involve?
In the regeneration phase of the Calvin cycle, what molecules are primarily produced?
In the regeneration phase of the Calvin cycle, what molecules are primarily produced?
What type of reactions does metabolism encompass within a living organism?
What type of reactions does metabolism encompass within a living organism?
How does penicillin disrupt bacterial cell walls?
How does penicillin disrupt bacterial cell walls?
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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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