Microbiology Chapter 7: Bacterial Growth and Culturing
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Questions and Answers

Which method is specifically used to provide sufficient oxygen for obligate aerobes?

  • Aeration (correct)
  • Candle Jar
  • Deep-freezing
  • Anaerobic Jar/Chamber

    • What is the primary function of an anaerobic jar/chamber?

  • It supports the growth of obligate anaerobes. (correct)
  • It provides a microaerophilic environment.
  • It is used for the storage of bacterial cultures.
  • It aids in the cultivation of obligate aerobes.

    • What characteristic of bacterial cultures is preserved through lyophilization?

  • Involves the use of antifreeze agents
  • Requires storage at -80 ºC
  • Allows for long-term room temperature storage (correct)
  • Demands constant refrigeration

    • Which of the following is NOT a method of preserving bacterial cultures?

    <p>Sterilization (B)</p> Signup and view all the answers

    Which method can identify bacteria using a seven-digit profile number derived from biochemical tests?

    <p>Analytical Profile Index (API) (A)</p> Signup and view all the answers

    What mechanism do some bacteria use to adapt to limited nutrients?

    <p>Endospore formation (B)</p> Signup and view all the answers

    Which of the following statements is true regarding sporulation?

    <p>It is initiated by a decrease in carbon or nitrogen levels. (A)</p> Signup and view all the answers

    Which of the following is NOT a type of bacterial interaction?

    <p>Commensal (A)</p> Signup and view all the answers

    What is quorum sensing primarily concerned with?

    <p>Gene expression based on cell density (B)</p> Signup and view all the answers

    Which component is NOT part of an endospore's core structure?

    <p>Lipids (B)</p> Signup and view all the answers

    What role does the cortex play in endospores?

    <p>Shielding against osmotic pressure (A)</p> Signup and view all the answers

    Which of the following best describes the relationship between bacteria in a synergistic interaction?

    <p>Both organisms benefit from the relationship. (B)</p> Signup and view all the answers

    Why do bacteria adjust their metabolism when nutrients are limited?

    <p>To maximize energy efficiency (B)</p> Signup and view all the answers

    What stimulates the activation of specific adaptive genes in bacteria during quorum sensing?

    <p>Accumulate of inducer molecules (B)</p> Signup and view all the answers

    What is the primary characteristic of bacteria in a biofilm?

    <p>Forming clusters that stick to each other (A)</p> Signup and view all the answers

    What percentage of bacterial infections in humans are attributed to biofilms?

    <p>Two-thirds (A)</p> Signup and view all the answers

    Which method involves spreading a diluted sample over the surface of an agar plate to obtain isolated colonies?

    <p>Streak Plate Method (B)</p> Signup and view all the answers

    In what industrial context are biofilms commonly associated?

    <p>Premise plumbing corrosion (D)</p> Signup and view all the answers

    How do bacteria within a biofilm contribute to genetic diversity?

    <p>By exchanging genetic material (C)</p> Signup and view all the answers

    What type of culture medium encourages the growth of specific organisms while suppressing others?

    <p>Selective media (B)</p> Signup and view all the answers

    What technique is used to prevent contamination when culturing bacteria?

    <p>Aseptic technique (D)</p> Signup and view all the answers

    Which type of medium has an unknown chemical composition and may vary between batches?

    <p>Complex medium (C)</p> Signup and view all the answers

    What observable characteristic is used to identify lactose fermenters on MacConkey agar?

    <p>Red colonies (C)</p> Signup and view all the answers

    What is a consequence of bacteria growing in close proximity within a biofilm?

    <p>They release factors to kill one another (D)</p> Signup and view all the answers

    What is one of the methods mentioned for isolating single bacterial cells?

    <p>Serial dilution (D)</p> Signup and view all the answers

    What component in mannitol salt agar indicates fermentation by pathogenic Staphylococcus aureus?

    <p>Phenol red (B)</p> Signup and view all the answers

    Which culture technique involves diluting and then plating samples to separate individual cells?

    <p>Pour plate method (D)</p> Signup and view all the answers

    What is the purpose of using enrichment media?

    <p>To allow for the growth of fastidious organisms (A)</p> Signup and view all the answers

    Which of the following correctly describes a characteristic of differential media?

    <p>Contains mannitol to test for fermentation (A)</p> Signup and view all the answers

    Flashcards

    Bacterial Growth and Division

    How bacteria increase in number through cell division.

    Adaptation to Limited Nutrients

    Bacteria adjust to limited nutrients by synthesizing more enzymes, changing metabolism, or forming endospores.

    Endospores

    Protective structures formed by some bacteria to survive harsh conditions.

    Sporulation

    The process of forming endospores.

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    Quorum Sensing

    Bacteria coordinating gene expression based on population density.

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    Bacterial Interactions

    How bacteria interact with each other.

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    Antagonistic Relationships

    Negative interactions between bacteria, like toxin production.

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    Synergistic Relationships

    Positive interactions between bacteria, like in bioluminescence.

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    Biofilm

    A community of microorganisms held together by a matrix of proteins, DNA, and sugars. They adhere to surfaces and can form intricate structures.

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    Antibiotic Resistance in Biofilms

    Bacteria within biofilms often exhibit resistance to antibiotics due to the protective matrix and slow growth rates.

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    Genetic Diversity in Biofilms

    The close proximity of bacteria in biofilms enables the exchange of genetic material, leading to increased diversity.

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    Biofilm Formation and Disease

    Biofilms are implicated in many bacterial infections in humans, contributing to antibiotic resistance and immune evasion.

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    Biofilms in Industry

    Biofilms can cause corrosion in plumbing systems and create unfavorable conditions in aquaculture.

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    Serial Dilution

    A technique used to isolate individual bacteria by diluting a sample multiple times to reduce the number of bacteria present.

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    Aseptic Technique

    A set of procedures used to prevent contamination of sterile substances or objects. This is crucial for culturing bacteria.

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    Streak Plate Method

    A technique for isolating pure cultures of bacteria by streaking a sample across the surface of an agar plate, diluting the bacteria with each streak, and allowing individual colonies to grow.

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    Pour Plate Method

    Isolation of pure cultures by mixing a diluted sample of bacteria with melted agar and pouring it into Petri dishes. Individual colonies grow within the agar.

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    Liquid Media

    A type of culture medium that is in a liquid state. Examples include nutrient broth.

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    Solid Media

    A type of culture medium that is solid, usually achieved by adding agar to a liquid medium. Petri plates and slant tubes are examples.

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    Selective Media

    Culture medium that encourages the growth of specific organisms while inhibiting the growth of others.

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    Differential Media

    Culture medium that allows the differentiation of bacteria based on their metabolic characteristics, often by changing color or pH.

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    Enrichment Media

    Culture medium that promotes the growth of specific organisms by providing them with the essential nutrients.

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    MacConkey Agar

    A selective and differential medium that inhibits gram-positive bacteria and differentiates lactose fermenters from non-fermenters.

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    Aeration

    A technique used to provide enough oxygen for aerobic bacteria to grow.

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    Candle Jar

    A method for growing microaerophilic bacteria, which need oxygen but at lower concentrations than air.

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    Anaerobic Jar

    A sealed container that removes oxygen and creates an environment suitable for obligate anaerobic bacteria.

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    API (Analytical Profile Index)

    A system used to identify bacteria based on their biochemical reactions to various tests.

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    Lyophilization

    A method for preserving bacteria by freeze-drying, which removes all water and allows long-term storage at room temperature.

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    Study Notes

    Lecture 9: Growth and Culturing of Bacteria - 2

    • Lecture focuses on bacterial growth, culturing, and factors affecting growth
    • Chapter 7 in a Microbiology textbook
    • Instructor: Qiang Chen, [email protected]

    Chapter Targets

    • Bacterial Growth and Division
    • Factors Affecting Bacterial Growth
    • Culturing Bacteria and Medium

    Adaptation to Limited Nutrients

    • Some bacteria synthesize more enzymes to absorb and process limited nutrients
    • Others develop the ability to utilize different nutrients (e.g., glucose to lactose)
    • Many organisms optimize nutrient metabolism efficiency; avoiding wasted energy during growth
    • Some bacteria form endospores to adapt to nutrient scarcity

    Sporulation

    • Endospores are formed in certain Gram-positive bacteria (Bacillus, Clostridium), and are a mechanism for survival, not reproduction
    • Characterized by a distinctive internal core structure comprised of RNA, protein, DNA, dipicolinic acid, and calcium ions.
    • A protective cortex layer surrounds this core, providing resilience against osmotic pressure.
    • A spore coat envelops the cortex making the endospore resistant to chemical damage
    • Sporulation response to environmental cues like lower carbon or nitrogen levels
    • Spores germinate into vegetative cells in suitable environments.
    • Sporulation differs from fungal spores in its formation, response signaling and role

    Sporulation Cycle

    • Cycle alternates between vegetative (growth) and sporulation (survival) modes
    • Factors triggering sporulation are environmental (e.g., low nutrient levels) or metabolic signals.

    Endospore Formation

    • An example of an important adaptation in bacteria to endure harsh conditions, such as starvation.

    Factors Affecting Bacterial Growth

    • The topic is presented as a slide title

    Bacterial Interactions

    • Organisms interact within various types of relationships:

      • Antagonistic (competitive)
      • Synergistic (cooperative)
      • Symbiotic

    • Competition between bacteria can lead to toxin production

    Quorum Sensing

    • Quorum: the minimum number of members required in an assembly to make proceedings valid.
    • Quorum sensing in bacteria: gene expression regulation in response to cell density changes.
    • A communication method to coordinate behavior in groups (large bacterial populations)
    • Signaling molecule concentration determines the expression of specific genes, influencing group behavior.
      • Signaling molecules (inducers) trigger events like food digestion or biofilm growth.

    Biofilms

    • Biofilm: a community of microorganisms where cells stick together and often attach to a surface.
    • Biofilm characteristics include:
      • Antibiotic resistance
      • Genetic exchange
      • Sensing and response to other organisms in the biofilm

    Biofilms in medicine, industry, and aquaculture

    • Two-thirds of infections involve biofilm formation in humans
    • Biofilms create antimicrobial tolerance and evade immune systems
    • Biofilms cause premise plumbing corrosion.
    • Biofilms affect aquaculture environments.

    Technological Approaches to Combat Biofilms

    • Approaches to overcome biofilm issues are discussed in this section:
    • Surface modification
    • Nanoparticles or small-molecule agents
    • Physical removal

    Biofilms in Wound Healing

    • Topical antimicrobial epoxy-tiglianes from the blushwood tree induce biofilm disruption, wound healing in acute and chronic skin wounds.

    Alcanivorax borkumensis Biofilms

    • This bacterium forms biofilms around oil droplets, but the exact role in oil degradation is discussed.
    • A morphological shift facilitates efficient oil degradation through interfacial tubulation.
    • The biofilm development leads to interfacial defects in the biofilm that improve biodegradation efficiency
    • Microbes modify the oil droplets to speed the process of biodegradation.

    Culturing Bacteria

    • Not all bacteria in natural environments can be grown in a laboratory setting.

    Types of Culture Media

    • Liquid media (broth) are common for growth
    • Solid media (agar, petri dishes, slant tubes).
    • Semi-solid media (0.5% agar) are useful in various applications.

    Culture Media Composition

    • Defined synthetic media: composition is precisely known
    • Complex media (chemically unspecified): composition varies, and isn't precisely known

    Culture Media Purposes

    • Selective media encourage a specific microorganism, while suppressing others.
    • Differential media lead to observable changes (color, pH) based on particular characteristics.
    • Enrichment media allow a target organism to thrive.

    Controlling Oxygen Content

    • Aeration sustains organisms that require oxygen
    • Candle jars support microaerophilic growth conditions
    • Anaerobic jars/chambers eliminate oxygen for anaerobic species cultivation

    Bacterial Identification

    • Gram staining is a method to differentiate bacterial species based on cell wall structure.
    • Morphology is the analysis of cell characteristics (shape, size).
    • Oxygen requirement (aerobes, anaerobes, facultative anaerobes) are essential classifications for bacterial identification.
    • Biochemical tests reveal additional traits.

    Methods of Performing Multiple Diagnostic Tests

    • Analytical Profile Index (API): A method to identify bacteria and yeast based on biochemical tests.

    Preserving Bacterial Cultures

    • Refrigeration: short-term (hours or days) storage
    • Deep-freezing: long-term storage after a freezing step
    • Lyophilization (freeze-drying): long-term, stable storage after freezing a liquid sample, and removing the water.

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    Lecture 9: Growth and Culturing of Bacteria - 2 PDF

    Description

    This quiz explores bacterial growth, factors affecting culturing, and the adaptation mechanisms of bacteria to limited nutrients. It covers key concepts such as sporulation and nutrient metabolism, focusing on the specifics outlined in Chapter 7 of a Microbiology textbook.

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