Microbiology Quiz: Heterocysts and Spores
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Questions and Answers

What is the primary function of heterocysts in Anabaena?

  • Oxygen production
  • Photosynthesis
  • Carbon source production
  • Nitrogen fixation (correct)
  • Which structural feature of heterocysts helps to protect them from oxygen?

  • Hydrophobic barrier (correct)
  • Polysaccharide layer
  • Photosystem II
  • Glycolipid layer
  • What type of cells are intercalated with heterocysts in Anabaena chains?

  • Vegetative cells (correct)
  • Identical heterocysts
  • Spores
  • Endospores
  • What metabolic characteristic is notably increased in heterocysts?

    <p>Respiration rate</p> Signup and view all the answers

    What occurs to photosystem II in heterocysts to facilitate their function?

    <p>Complete loss</p> Signup and view all the answers

    What is the significance of dipicolinic acid (DPA) during spore germination?

    <p>It promotes spore core hydration.</p> Signup and view all the answers

    Which of the following components is responsible for the lethal toxin of anthrax?

    <p>Lethal factor (LF)</p> Signup and view all the answers

    What initiates the process of spore germination after dormancy?

    <p>DPA release</p> Signup and view all the answers

    Which plasmid contains genes for toxin production in anthrax?

    <p>pXO1</p> Signup and view all the answers

    What is the main role of the capsule in vegetative cells of anthrax?

    <p>It protects the cell from phagocytosis.</p> Signup and view all the answers

    Which system in Pseudomonas aeruginosa uses AHL autoinducers?

    <p>Rhl system</p> Signup and view all the answers

    Which of the following statements describes Myxobacteria fruiting body formation?

    <p>It involves multicellular development via directed growth.</p> Signup and view all the answers

    What characteristic distinguishes Myxospores from endospores?

    <p>Myxospores are less resistant than vegetative cells.</p> Signup and view all the answers

    What type of developmental cycle does Bacillus endospore formation represent?

    <p>Unicellular and cell-cycle independent</p> Signup and view all the answers

    What is the purpose of estimating transcription factor (TF) activities in network inference?

    <p>To analyze gene expression profiles</p> Signup and view all the answers

    Which nutritional factor is associated with the GerA receptor in Bacillus subtilis germination?

    <p>L-Alanine</p> Signup and view all the answers

    In the context of Bacillus subtilis, what is the consequence of spore germination on optical density?

    <p>Loss of optical density</p> Signup and view all the answers

    What do germination receptors in Bacillus subtilis function as?

    <p>Nutrient-gated ion channels</p> Signup and view all the answers

    During which phase does the outgrowth of a spore in Bacillus subtilis occur?

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

    According to the network inference process, which option correctly matches one of the activities related to TFs?

    <p>Regulatory gene expression</p> Signup and view all the answers

    What is the primary function of nitrogenase in cyanobacteria?

    <p>Fixes atmospheric N2 to NH4+</p> Signup and view all the answers

    Which of the following statements about cyanobacteria is accurate?

    <p>They primarily use sunlight for energy.</p> Signup and view all the answers

    How does O2 interfere with nitrogen fixation in cyanobacteria?

    <p>It inactivates the nitrogenase enzyme.</p> Signup and view all the answers

    Which cyanobacteria can utilize atmospheric N2 as a nitrogen source?

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

    What characterizes the process of sporulation in Streptomycetes?

    <p>Cell-cycle dependent growth and differentiation</p> Signup and view all the answers

    What is the significance of the GS/GOGAT pathway in nitrogen assimilation?

    <p>It converts nitrogen compounds into glutamate and glutamine.</p> Signup and view all the answers

    Which of the following is a characteristic feature of filamentous cyanobacteria?

    <p>They can form heterocysts for nitrogen fixation.</p> Signup and view all the answers

    What does the GC content in cyanobacterial genomes indicate?

    <p>Thermal stability of the DNA</p> Signup and view all the answers

    What characteristic makes Mycobacterium tuberculosis difficult to stain?

    <p>It has a waxy layer composed of mycolic acids.</p> Signup and view all the answers

    How do mycobacteria primarily divide?

    <p>Asymmetrically by depositing new cell wall material at the tips.</p> Signup and view all the answers

    What did Rudolf Virchow discover about the effects of tuberculin?

    <p>It activated latent bacteria instead of killing them.</p> Signup and view all the answers

    What does the term 'acid fast' refer to in the context of Mycobacterium tuberculosis?

    <p>The bacterium's resistance to decolorization by acid after staining.</p> Signup and view all the answers

    What role does the mycomembrane play in mycobacterial cells?

    <p>It is impermeable, helping in antibiotic resistance.</p> Signup and view all the answers

    What is the significance of mycolic acids in mycobacterial cells?

    <p>They contribute to the bacterium's staining characteristics and impermeability.</p> Signup and view all the answers

    Study Notes

    Endospore Formation

    • Endospores are dormant bacterial cells
    • Highly resistant to harsh conditions like heat, desiccation, chemicals (bleach, chloroform), enzymes (lysozyme), and antibiotics. UV radiation.
    • A spore is a dormant cell.
    • Protective layers: Cortex (multi-layered coat of ~80 proteins)
    • First publication on endospore formation (1876)
    • Types of spore-forming bacteria: Bacillus, Listeria, Staphylococcus, and Clostridium.
    • Specific diseases caused by spore-forming bacteria/examples: Anthrax (Bacillus anthracis), food poisoning (Bacillus cereus, Listeria monocytogenes), colitis and diarrhea (Clostridium difficile), botulism (Clostridium botulinum), tetanus (Clostridium tetani)

    Sporulation Cycle

    • Sporulation is the process of forming an endospore.
    • Germination is the process of the endospore returning to a vegetative cell.
    • Spores are formed in response to nutrient limitation.
    • Spores germinate when favorable conditions are encountered.
    • The spore serves as a delivery vehicle.
    • The vegetative cell causes the disease.

    Spo0A

    • Spo0A is the master regulator of sporulation.
    • It's a response regulator.
    • It has a regulatory domain (Asp phosphorylation site) and an effector domain (DNA binding).
    • Spo0A is activated by a phosphorelay.

    Regulation of the phosphorelay (of Spo0A)

    • The phosphorelay is regulated by redox state, DNA damage, and cell density (quorum sensing).
    • Key proteins involved include KinA, KinB, KinC, Spo0F, Spo0B and Spo0E (phosphatase).

    Asymmetric Division

    • Asymmetric division is the process by which a cell divides unevenly, producing a different fate for each daughter cell.
    • Spores are formed via asymmetric cell division.

    Sigma Factors in B. subtilis

    • B. subtilis has 18 sigma factors.
    • 1 primary sigma factor and 17 other alternative factors.
    • These factors are involved in different stages or cell processes.
    • Examples of primary factors: general stress response, motility, chemotaxis, autolysis, spore formation (early), spore formation (late), stationary phase and a few examples of some alternative factors: antimicrobial resistance and cell envelope stress.

    Compartmentalization of Gene Expression

    • Gene expression is compartmentalized in spore-forming bacteria.
    • Different sigma factors control gene expression in different regions of the cell.

    σF Inhibition/Activation

    • σF inhibition involves the anti-σ factor SpoIIAB or AB.
    • σF activation is triggered by dephosphorylation of SpollAA by SpollE.
    • σF is active after dephosphorylation of the anti-σ factor.
    • σF is synthesized as pro-σF and then activated by proteolysis.

    Biofilms

    • Biofilms are matrix-encased microbial communities.
    • They are found at interfaces of solid-air, solid-liquid and air-liquid surfaces.
    • Biofilms can contain more than one microbial species.
    • Biofilms formation shows some benefits like protection, colonization and communal behavior.
    • Steps in biofilm formation: adhesion, colonization, growth and matrix formation and sometimes detachment.

    Anthrax

    • Bacillus anthracis is a Gram-positive, rod-shaped bacterium.
    • It's a Category A bioterror agent that causes anthrax.
    • Spores are the delivery vehicle (cause disease).
    • Vegetative cells cause disease symptoms.
    • Toxins (PA, LF, EF) are important virulence factors produced by vegetative cells.

    C. difficile

    • C. difficile is a Gram-positive, anaerobic, spore-forming rod-shaped bacterium.
    • Pathogenic C. difficile produces toxins (TcdA and TcdB) that contribute to the symptoms of pseudomembranous colitis.
    • C. difficile is a nosocomial agent that causes colitis and diarrhea.
    • Antibiotic treatment can trigger the proliferation of C. difficile.
    • C. difficile infections are commonly linked to hospitals and clinics.

    Myxobacteria

    • Myxobacteria can form fruiting bodies, which are specialized structures during unfavorable conditions.
    • Myxobacteria fruiting bodies contain dormant spores, which are more resistant than vegetative cells.
    • Important for predation.
    • Other factors: Mounded aggregates, Lysis of prey, Swarm.
    • Myxobacteria show diverse spore-bearing structures.

    Bdellovibrio

    • Bdellovibrio bacteriovorus is a Gram-negative, parasitic bacterium.
    • It feeds on other bacteria (predation).
    • The cycle involves attachment, penetration of the prey's wall, reproduction within the prey, release of progenies and eventually prey lysis.

    Antibiotics

    • Chemical agents that kill or inhibit the growth of microbes.
    • Natural products or synthetic drugs.
    • Common uses: combating bacterial infections.
    • Common targets of antibiotics: Cell wall synthesis, DNA synthesis, Protein synthesis, RNA synthesis, Folic acid metabolism.
    • Important applications: Treating infectious diseases, controlling bacteria and some fungi.
    • Types of action: Bacteriostatic, Bacteriocidal, Fungicidal, Viricidal.

    Antimicrobial resistance

    • Resistance to antibiotics arises through genetic mechanisms such as: Target site modifications, Inactivation of antibiotics by hydrolysis, Reduction in membrane permeability, and Alternative metabolic pathways.
    • Pathogens can acquire resistance mechanisms through vertical or horizontal evolution. Vertical evolution is through inherited mutations while horizontal evolution is via plasmids, transduction, transformation etc.
    • Resistance mechanisms include modifications in the antibiotic target, changes in the target site, reduced permeability and increased efflux and alternative pathways.

    Bacterial Phylogeny

    • A hierarchical classification highlighting the evolutionary relationships between taxa or groups of similar organisms.

    Cyanobacteria

    • Photosynthetic bacteria that fix carbon and produce oxygen.
    • An important factor: nitrogen fixation (conversion of N₂ to NH⁴⁺) is inhibited by O₂.

    Nitrogen Fixation

    • The process that converts atmospheric nitrogen into ammonia using nitrogenase.
    • Important for the production of organic nitrogen in cells.

    Mycobacteria

    • Gram-positive bacteria, with high GC content.
    • Mycobacterium tuberculosis is a pathogen that causes tuberculosis.
    • Mycobacterium leprae causes leprosy.
    • Their thick cell walls and mycolic acids make them very resistant to various agents.

    Specific Details about Microorganisms

    • Include details about bacterial shapes, sizes and traits (whether they are Gram-positive or Gram-negative etc.).

    Specific Infections

    • Include details about particular diseases/symptoms and causes of illness (e.g. tetanus, botulism, anthrax, TB, Lyme disease, etc..).

    Important scientists and their discoveries

    • Provide information about their impact on scientific breakthroughs or on treatment approaches for infectious diseases.

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    Description

    Test your knowledge on the functions and characteristics of heterocysts in Anabaena, the mechanics of spore germination, and the biology of anthrax. This quiz covers essential microbial processes and the unique features of different bacterial cells. Challenge yourself with questions on metabolic adaptations and toxin production.

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