Lesson 2: Cell Surface Structures
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Questions and Answers

What triggers the process of sporulation in Bacillales and Clostridiales?

  • Limiting nutrients (correct)
  • Availability of amino acids
  • Excess water
  • High temperatures

    • Which layer is NOT always present in the structure of an endospore?

  • Endospore coat
  • Exosporium (correct)
  • Cortex
  • Inner membrane

    • What is the function of small acid-soluble spore proteins (SASPs) during sporulation?

  • Assist in endospore germination
  • Aid in cellular division
  • Bind to DNA and protect from damage (correct)
  • Facilitate nutrient absorption

    • In which step of the sporulation cycle does the cortex form?

    <p>Cortex formation</p> Signup and view all the answers

    What is the primary reason for the toughness of endospores?

    <p>Dehydration of the core</p> Signup and view all the answers

    Which staining method is used to visualize endospores?

    <p>Malachite green stain</p> Signup and view all the answers

    What happens during the outgrowth step of germination?

    <p>A vegetative cell emerges</p> Signup and view all the answers

    Which component of the endospore contains DNA and ribosomes?

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

    What is the primary function of capsules and slime layers in bacterial cells?

    <p>Mediating attachment and protection</p> Signup and view all the answers

    Which type of pili is specifically involved in genetic exchange during conjugation?

    <p>F pilus</p> Signup and view all the answers

    What distinguishes a microcapsule from a regular capsule?

    <p>It cannot be seen by light microscopy</p> Signup and view all the answers

    Which type of structure resembles a tiny grappling hook and is used to anchor cells?

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

    What is the primary function of gas vesicles in bacteria?

    <p>Buoyancy for floating</p> Signup and view all the answers

    What substance is most commonly found as inclusion bodies in prokaryotes?

    <p>Poly-β-hydroxybutyric acid (PHB)</p> Signup and view all the answers

    Which type of endospore is produced only by specific groups of bacteria?

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

    Which of the following is a characteristic of magnetosomes?

    <p>They orient bacteria within a magnetic field</p> Signup and view all the answers

    What role does glycogen play in bacterial cells?

    <p>Reservoir of carbon and energy</p> Signup and view all the answers

    What is the primary function of flagella in bacteria?

    <p>Swimming motility</p> Signup and view all the answers

    Which of the following statements about fimbriae is true?

    <p>They are thin protein extensions allowing attachment.</p> Signup and view all the answers

    Which type of flagellation involves flagella anchored at both ends of the cell?

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

    How do flagella change direction when swimming?

    <p>By changing the rotation direction</p> Signup and view all the answers

    What drives the rotation of archaella in archaea?

    <p>Hydrolysis of ATP</p> Signup and view all the answers

    What component of the flagellar motor generates torque?

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

    Which component of the flagellum is responsible for connecting the filament to the motor?

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

    Which of the following describes a tuft of flagella?

    <p>A group of flagella at one end</p> Signup and view all the answers

    What protein composes the filament of bacterial flagella?

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

    What is the primary movement type of cells with cilia?

    <p>Sweeping food into oral cavities</p> Signup and view all the answers

    What characteristic distinguishes the movement speed of archaella compared to flagella?

    <p>Smaller diameter leading to reduced torque</p> Signup and view all the answers

    What mechanism do peritrichously flagellated bacteria use to navigate toward attractants?

    <p>Biased random walk</p> Signup and view all the answers

    What type of ciliary movement is characterized by hook-like movements?

    <p>Unciform ciliary movement</p> Signup and view all the answers

    How do polarly flagellated bacteria differ in their movement compared to peritrichously flagellated bacteria?

    <p>They do not exhibit tumbling.</p> Signup and view all the answers

    Which of the following forms of taxis is primarily associated with a response to light?

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

    Which cytoskeletal component is described as rope-like assemblies of fibrous polypeptides?

    <p>Intermediate filaments</p> Signup and view all the answers

    What is the role of chemoreceptors in bacteria?

    <p>To sense attractants and repellents</p> Signup and view all the answers

    What characterizes twitching motility in microbial locomotion?

    <p>Movement from ATP hydrolysis using type IV pili</p> Signup and view all the answers

    Which of the following describes gliding motility?

    <p>Smooth motion along the cell axis without external structures</p> Signup and view all the answers

    Which form of taxis involves a bacterium responding to ionic strength?

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

    What defines chemotaxis in microbial movement?

    <p>Directed movement towards a chemical stimulus</p> Signup and view all the answers

    In terms of surface motility, what is true for twitching compared to swimming motility?

    <p>Surface motility is considerably slower than swimming motility.</p> Signup and view all the answers

    Which organisms typically exhibit gliding motility?

    <p>Myxobacteria and flavobacterium</p> Signup and view all the answers

    What type of internal movement is governed by actin filaments and the cytoskeleton?

    <p>Cytoplasmic streaming</p> Signup and view all the answers

    Study Notes

    Cell Surface Structures

    • Capsules and Slime Layers

      • Composed of polysaccharides; facilitate attachment, protection, and environmental alteration.
      • Biofilms form on solid surfaces from thick layers of slime.
      • Capsules are organized, visible via light and electron microscopy, and stain with India ink.
      • Slime layers are loosely attached, deformed easily, detectable in colonies, and enriched in a common matrix.

    • Fimbriae, Pili, and Hami

      • Pili are thin protein filaments, aiding in surface attachment, biofilm formation, and liquid pellicles; all gram-negative bacteria produce them.
      • Types of Pili:
        • Conjugative pili enable genetic exchange.
        • Electrically conductive pili assist in metabolic processes by conducting electrons.
        • Type IV pili facilitate adhesion and motility, important for pathogens like cholera and gonorrhea.
        • F pilus (sex pilus) serves in genetic material transfer during mating.
      • Fimbriae are short pili primarily for attachment.
      • Hami resemble grappling hooks, aiding Archaea in forming networked biofilms.

    Cell Inclusions

    • Often visible under light microscopy, serve as storage and structural components.

    • Carbon Storage Polymers

      • Poly-β-hydroxybutyric acid (PHB) is the main prokaryotic inclusion, synthesized from excess carbon.
      • Glycogen, a glucose polymer, acts as a carbon and energy reservoir.

    • Polyphosphate, Sulfur, and Carbonate Minerals

      • Polyphosphate may store inorganic phosphate for nucleic acid and phospholipid biosynthesis.
      • Sulfur bacteria oxidize sulfur compounds, crucial for energy metabolism.
      • Carbonate materials are formed by cyanobacteria, with Gloeomargarita identified for producing specific granules.

    • Gas Vesicles

      • Confer buoyancy, allowing microbes to float and position optimally in water.
      • Composed of conically shaped vesicles that are impermeable to water, allowing gas permeability.
      • Bloom is a mass accumulation of gas-vesiculate microbes, typically observed in sunlight-rich environments.

    • Magnetosomes

      • Contain magnetic iron oxides, aiding bacteria in orientation along magnetic fields (magnetotaxis).
      • Exhibit various shapes, primarily spiked or rectangular.

    Endospores

    • Unique spores produced by gram-positive Bacillales and Clostridiales, enabling survival in harsh conditions.
    • Cycle involves: vegetative cell → endospore → vegetative cell; triggered by nutrient limitation for sporulation.
    • Structure includes multiple protective layers and SASPs for DNA protection against UV and desiccation.
    • Germination occurs upon nutrient availability and involves activation, germination, and outgrowth phases.

    Cell Locomotion

    • Cells exhibit two primary movement types: swimming and gliding, with taxis directing movement towards or away from stimuli.

    • Flagella provide swimming motility, varying in structure and movement based on their location and number on the cell.

      • Speed reaches up to 60 cell-lengths/sec, rotating in a clockwise (CW) or counterclockwise (CCW) manner for directional change.
      • Types include polar (located at one/both ends) and peritrichous (surrounding the entire cell).

    • Flagellum Structure

      • Comprises filament, hook, and motor components that rotate to propel the cell.

    • Archaella

      • Similar to flagella but found in archaea, rotate using ATP hydrolysis, and possess different structural proteins.

    Cilia

    • Short hair-like structures facilitate motility and food acquisition, powered by ATP.
    • Display four types of movement: pendulus, unciform, infundibuliform, and undulant.

    Cytoskeletal Components

    • Intermediate Filaments support nuclear and plasma membranes.
    • Microtubules are made from tubulin proteins, forming hollow structures essential for cell shape and transport.

    Microbial Locomotion

    • Internal movement, via cytoplasmic streaming, is guided by the cytoskeleton.

    • External motility features pseudopodia, cilia, and flagella for movement.

    • Surface Motility

      • Twitching involves type IV pili, moving cells forward through attachment and retraction, occurring in groups.
      • Gliding offers smooth, continuous movement along the cell's length.

    Chemotaxis

    • Directed movement in response to chemical stimuli, observed in bacterial swimming.

    • Two types of rotation: runs (smooth swimming) and tumbles (random jiggling), enabling biased random walks towards attractants.

    • Additional Types of Taxis

      • Phototaxis (light response), osmotaxis (ionic strength), hydrotaxis (water availability), aerotaxis (response to O2), and magnetotaxis (interaction with magnetic fields) aid microbial navigation in their environments.

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    Description

    Test your knowledge on cell surface structures, including capsules and slime layers. This quiz covers their composition, functions, and roles in biofilm formation. Perfect for students of biology looking to reinforce their understanding of cell structures.

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