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Questions and Answers
Which of the following is primarily involved in the synthesis of microbial proteins?
Which of the following is primarily involved in the synthesis of microbial proteins?
- Carbohydrates
- Nucleic acids
- Amino acids (correct)
- Lipids
What type of metabolism generates energy without the use of oxygen?
What type of metabolism generates energy without the use of oxygen?
- Fermentation (correct)
- Anaerobic respiration (correct)
- Photophosphorylation
- Aerobic respiration
Which molecule serves as the primary energy currency in microbial cells?
Which molecule serves as the primary energy currency in microbial cells?
- FADH2
- ATP (correct)
- NADH
- DNA
In microbial metabolism, which of the following processes utilizes light energy?
In microbial metabolism, which of the following processes utilizes light energy?
Which type of biochemical reaction is characterized by the addition of electrons?
Which type of biochemical reaction is characterized by the addition of electrons?
Which macromolecule is primarily responsible for catalyzing biochemical reactions in microorganisms?
Which macromolecule is primarily responsible for catalyzing biochemical reactions in microorganisms?
What is the primary byproduct of fermentation in many microbial species?
What is the primary byproduct of fermentation in many microbial species?
Which of the following is NOT a function of lipids in microbial cells?
Which of the following is NOT a function of lipids in microbial cells?
Which of the following processes breaks down glucose in the absence of oxygen?
Which of the following processes breaks down glucose in the absence of oxygen?
What phase of microbial growth is characterized by little to no increase in cell numbers as the culture adjusts to a new environment?
What phase of microbial growth is characterized by little to no increase in cell numbers as the culture adjusts to a new environment?
Which phase of microbial growth shows the maximum growth rate due to active cell division?
Which phase of microbial growth shows the maximum growth rate due to active cell division?
If the generation time (g) is calculated using the formula g = t/n, what do the variables t and n represent?
If the generation time (g) is calculated using the formula g = t/n, what do the variables t and n represent?
What does the term 'culture density' refer to in microbial growth analysis?
What does the term 'culture density' refer to in microbial growth analysis?
How does environmental condition affect microbial generation times?
How does environmental condition affect microbial generation times?
What does the doubling time in bacterial growth represent?
What does the doubling time in bacterial growth represent?
In the context of bacterial division, what does FtsZ protein primarily assist with?
In the context of bacterial division, what does FtsZ protein primarily assist with?
What does the generation time indicate in microbial growth?
What does the generation time indicate in microbial growth?
Which stage of the growth curve represents a period of slow growth where bacteria adapt to their environment?
Which stage of the growth curve represents a period of slow growth where bacteria adapt to their environment?
What can happen to microbial populations when environmental conditions become unfavorable?
What can happen to microbial populations when environmental conditions become unfavorable?
What is the main characteristic of the exponential growth phase in microbial populations?
What is the main characteristic of the exponential growth phase in microbial populations?
How does the addition of nutrients typically affect microbial populations during growth?
How does the addition of nutrients typically affect microbial populations during growth?
What does the term 'Measuring Microbial Populations' refer to?
What does the term 'Measuring Microbial Populations' refer to?
What is a potential consequence of salt or freshwater eutrophication?
What is a potential consequence of salt or freshwater eutrophication?
What characterizes the exponential growth phase in microbial populations?
What characterizes the exponential growth phase in microbial populations?
What occurs during the stationary phase of microbial growth?
What occurs during the stationary phase of microbial growth?
Which of the following is a reason why cells are less susceptible to antibiotics during the stationary phase?
Which of the following is a reason why cells are less susceptible to antibiotics during the stationary phase?
What is the primary reason persister cells are significant in chronic infections?
What is the primary reason persister cells are significant in chronic infections?
How is the generation time commonly represented in microbial growth curves?
How is the generation time commonly represented in microbial growth curves?
What method is used to measure the turbidity of a microbial culture?
What method is used to measure the turbidity of a microbial culture?
What is the purpose of using serial dilutions in microbial counting?
What is the purpose of using serial dilutions in microbial counting?
Why is the pour plate method beneficial in microbial counting?
Why is the pour plate method beneficial in microbial counting?
What is a significant limitation of direct cell count using a Petroff-Hauser chamber?
What is a significant limitation of direct cell count using a Petroff-Hauser chamber?
What role do biofilms play in microbial communities?
What role do biofilms play in microbial communities?
In measuring microbial populations, what is the measure known as 'CFU'?
In measuring microbial populations, what is the measure known as 'CFU'?
Which factor most directly affects the rate of microbial growth in a culture?
Which factor most directly affects the rate of microbial growth in a culture?
What does an increase in optical density (OD) indicate in a microbial culture?
What does an increase in optical density (OD) indicate in a microbial culture?
Study Notes
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Microbial Growth
- Bacterial cells multiply through binary fission, which involves DNA replication, partitioning of cell components, and cytokinesis.
- Cytokinesis is directed by protein FtsZ, forming a Z ring on the cytoplasmic membrane, defining the division plane.
- Generation time or doubling time refers to the time taken for the population to double in size.
- Growth curve is a graphical representation of microbial growth in a closed culture over time.
- Four distinct phases can be observed during bacterial growth in a closed culture:
- Lag phase: Minimal cell growth, the cells are adjusting to the environment, repairing damage, and synthesizing proteins.
- Log (exponential) phase: Maximum growth rate where cells divide actively with short generation times.
- Stationary phase: Growth slows down, cell death equals cell division due to limited nutrients and waste accumulation.
- ** Death phase:** Number of dying cells exceeds the number of dividing cells, causing an exponential decline in population.
- Microbial growth can be measured using direct and indirect methods:
- Direct methods: Count bacterial cells directly using a microscope, plate count, filtration, or the most probable number (MPN) method.
- Indirect methods: Measure turbidity, dry weight, or metabolic activity.
- Direct cell count uses a Petroff-Hauser chamber to observe and count cells under a microscope.
- Plate counts determine the number of living cells that can form colonies on agar plates, and the results are expressed as colony-forming units (CFU/mL).
- Serial dilution is used to obtain the appropriate number of colonies on the plates (30-300 CFUs) for accurate counting.
- Membrane filtration method is used for samples with low bacterial density, where the bacteria are collected on a filter and then transferred to an agar plate for counting.
- Turbidity is a measure of cloudiness, while spectrophotometer analyzes light scattering by bacteria to assess cell density.
- Biofilms are microbial communities embedded in extracellular polymeric substances (EPS). EPS provides structural integrity and protects bacteria from harmful environmental conditions.
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