L2 - Bacterial Growth and Physiology
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Questions and Answers

What defines essential growth factors for bacteria?

  • They enhance growth without being necessary.
  • They are indispensable for bacterial growth. (correct)
  • They can be synthesized by the bacteria.
  • They are required in minute quantities.

    • Which culture technique is primarily used to isolate a single colony of bacteria?

  • Stroke culture
  • Lawn culture
  • Streak culture (correct)
  • Pour plate

    • What is the main purpose of lawn culture?

  • To test antibiotic sensitivity. (correct)
  • To isolate bacteria in streaks.
  • To culture bacteria for sterility tests.
  • To prepare bacterial antigens.

    • What does the stab culture technique involve?

    <p>Puncturing the medium with a wire.</p> Signup and view all the answers

    Which culture technique is suitable for maintaining a stock culture?

    <p>Stab culture</p> Signup and view all the answers

    In which method does the inoculum get stretched out across the surface of the agar plate?

    <p>Spread plate</p> Signup and view all the answers

    Which of the following statements about growth factors is false?

    <p>Both types are synthesized by the bacteria.</p> Signup and view all the answers

    Which characteristic is unique to pour plate culture?

    <p>It allows for the formation of discrete colonies on the agar surface.</p> Signup and view all the answers

    What is the primary process through which bacteria multiply?

    <p>Binary fission</p> Signup and view all the answers

    During which phase of the bacterial growth curve does the number of new cells produced equal the number of cells that die?

    <p>Stationary phase</p> Signup and view all the answers

    What is the generation time for Escherichia coli?

    <p>20 minutes</p> Signup and view all the answers

    What type of cell count includes both living and dead cells?

    <p>Total cell count</p> Signup and view all the answers

    Which bacterial species has the longest generation time among the following?

    <p>Mycobacterium leprae</p> Signup and view all the answers

    What characterizes the lag phase of the bacterial growth curve?

    <p>High metabolic activity without cell division</p> Signup and view all the answers

    Which of the following conditions are bacteria most likely to face during the stationary phase?

    <p>Toxic product accumulation</p> Signup and view all the answers

    What is true about the log phase in bacterial growth?

    <p>Rapid cell division occurs</p> Signup and view all the answers

    What characteristic defines mesophilic bacteria?

    <p>They prefer temperatures between 25ºC and 40ºC.</p> Signup and view all the answers

    Which type of bacteria requires the presence of oxygen for growth?

    <p>Strict aerobes</p> Signup and view all the answers

    Which of the following statements about osmotic effects on bacteria is true?

    <p>Bacterial cell walls provide mechanical strength against osmotic stress.</p> Signup and view all the answers

    What effect does drying have on bacterial cells?

    <p>It is lethal to most cells.</p> Signup and view all the answers

    How are acidophiles classified concerning pH levels?

    <p>They prefer acidic pH conditions.</p> Signup and view all the answers

    Which of the following is a requirement for bacteria to grow and multiply?

    <p>A nitrogen source and inorganic salts</p> Signup and view all the answers

    Which type of bacteria can utilize atmospheric CO2 and N2 for growth?

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

    Which of the following types of radiation is lethal to bacteria?

    <p>X rays and gamma rays</p> Signup and view all the answers

    Study Notes

    Learning Objectives

    • Classify bacteria based on growth requirements with examples.
    • Describe the process and stages of bacterial growth.
    • Discuss the essential requirements for bacterial growth.

    Bacterial Growth

    • Growth refers to an increase in cell components leading to population multiplication.
    • Bacteria reproduce by binary fission, resulting in generation time.
    • Example: E. coli (20 min), Mycobacterium tuberculosis (20 hours), Mycobacterium leprae (20 days).

    Bacterial Counts

    • Bacterial growth can be assessed by:
      • Total cell count: includes living and dead cells.
      • Viable cell count: only living cells.
    • Counting methods: direct counting using microscopy techniques.

    Bacterial Growth Curve

    • Involves tracking bacterial numbers over time in a nutrient medium.
    • Phases of the growth curve:
      • Lag Phase: Adaptation period, no cell division, metabolic activity present.
      • Log Phase: Rapid cell division, antibiotics most effective during this stage.
      • Stationary Phase: Balance of new cells produced and dying cells due to nutrient depletion.
      • Death Phase: Decline in viable bacteria numbers.

    Factors Affecting Bacterial Growth

    • Nutrition: Essential for growth.
    • Temperature: Classified into mesophilic (25-40ºC), thermophilic (55-58ºC), and psychrophilic (below 20ºC).
    • Oxygen Requirement:
      • Strict aerobes: require oxygen.
      • Strict anaerobes: cannot tolerate oxygen.
      • Microaerophiles: require low levels of oxygen.
      • Facultative anaerobes: can grow with or without oxygen.
    • H-ion Concentration:
      • Neutrophiles: pH 7.2-7.6.
      • Acidophiles: thrive in acidic conditions.
      • Alkalophiles: prefer alkaline environments.
    • Moisture: Essential for protoplasm; drying is lethal.
    • Osmotic Effects: Bacteria may tolerate osmotic variations due to cell wall strength.
    • Radiation: X and gamma rays can be lethal.
    • Mechanical Stress: High-stress conditions can cause cell lysis.

    Bacterial Nutrition

    • Water comprises 80% of bacterial cell weight.
    • Essential nutrients include carbon, nitrogen, and inorganic salts.
    • Carbon-based classification:
      • Autotrophs: Synthesize own organic compounds.
      • Heterotrophs: Depend on preformed organic compounds for growth.

    Growth Factors

    • Some bacteria require organic compounds in small amounts for growth.
      • Essential factors: Required for growth.
      • Accessory factors: Enhance growth but are not strictly necessary.

    Basic Bacterial Techniques

    • Streak Culture: Isolates single colonies using a loop on an agar plate.
    • Lawn Culture: Produces uniform growth; used for antibiotic testing and vaccine preparation.
    • Stroke Culture: Grows bacteria in agar slants for diagnostic tests.
    • Stab Culture: Created by puncturing medium to maintain stock culture.
    • Pour Plate Culture: Helps assess bacterial counts by mixing with liquid agar before solidifying.
    • Spread Plate Culture: Distributes bacteria evenly across an agar surface.

    Liquid Culture

    • Inoculated via loops or pipettes, preferred for when large yields are necessary, such as blood cultures and sterility tests.

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    L2 - Bacterial Growth and Physiology.pptx

    Description

    This quiz covers bacterial growth and physiology, focusing on classifying bacteria based on their growth requirements. Students will learn to describe the concept of bacterial growth and discuss various factors affecting it with suitable examples. Prepare to deepen your understanding of essential microbiology topics.

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