Bacterial Morphology and Cell Wall
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Questions and Answers

What is the shape of a coccus?

  • Oval
  • Rod-shaped
  • Spherical (correct)
  • Clusters

    • What shape are bacillus bacteria?

    Rod shaped

    What is a coccobacillus?

    Oval bacterium that is intermediate between the coccus and bacillus forms

    What is a diplococcus?

    <p>A bacterium that occurs as pairs of cocci</p> Signup and view all the answers

    Define streptococcus.

    <p>A bacterium that occurs as chains of cocci</p> Signup and view all the answers

    What is a staphylococcus?

    <p>A bacterium that occurs as clusters of cocci</p> Signup and view all the answers

    What is a tetrad?

    <p>Clusters of four cocci</p> Signup and view all the answers

    What is the glycocalyx formed by?

    <p>Capsule or slime layer polysaccharide with glycoproteins</p> Signup and view all the answers

    Which of the following is NOT a function of the glycocalyx?

    <p>Enhances antibiotic resistance</p> Signup and view all the answers

    What is the structure of the cell wall in bacteria?

    <p>Semi rigid cross linked peptidoglycan (murein)</p> Signup and view all the answers

    What does Gram staining indicate for Gram-positive bacteria?

    <p>Retains violet stain</p> Signup and view all the answers

    How thick is the cell wall of Gram-positive bacteria?

    <p>~25 layers of peptidoglycan thick</p> Signup and view all the answers

    How thick is the cell wall of Gram-negative bacteria?

    <p>~2 layers of peptidoglycan thick</p> Signup and view all the answers

    What is the periplasmic space?

    <p>Space between the cytoplasmic membrane and outer membrane in Gram-negative bacteria</p> Signup and view all the answers

    What composes the outer membrane of Gram-negative bacteria?

    <p>Phospholipids and lipopolysaccharides (LPS)</p> Signup and view all the answers

    What is LPS O antigen?

    <p>Antigen &amp; Immunogen composed of carbohydrate units</p> Signup and view all the answers

    What is antigenic variation?

    <p>Shifts in surface O antigens on infectious organisms</p> Signup and view all the answers

    What connects O antigen to lipid A?

    <p>LPS core polysaccharide</p> Signup and view all the answers

    What is lipid A?

    <p>Lipid embedded in the outer phospholipid layer of the outer membrane</p> Signup and view all the answers

    What are exotoxins?

    <p>Proteins secreted by living bacteria</p> Signup and view all the answers

    What is an endotoxin?

    <p>Structural lipopolysaccharide - lipid A</p> Signup and view all the answers

    What are teichoic and lipoteichoic acids?

    <p>Virulence factors only found within the peptidoglycan layers of Gram-positive bacteria</p> Signup and view all the answers

    What is the function of flagella in bacteria?

    <p>Motility/taxis</p> Signup and view all the answers

    What are pili?

    <p>Hair-like protein structures associated with the cell membrane</p> Signup and view all the answers

    What are endospores?

    <p>Dormant stage produced predominantly by Gram-positive bacteria</p> Signup and view all the answers

    What does fosfomycin block during bacterial cell wall synthesis?

    <p>Blocks MurA during formation of NAG</p> Signup and view all the answers

    What does D-cycloserine interfere with?

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

    What does daptomycin interfere with?

    <p>Membrane polarization</p> Signup and view all the answers

    What do oxacillin and penicillins target?

    <p>The transpeptidase crosslinking</p> Signup and view all the answers

    Monotrichous means __________.

    <p>-------(____)</p> Signup and view all the answers

    Lophotrichous means __________.

    <p>=====(______ ) Multiple flagella on one pole</p> Signup and view all the answers

    Amphitricous means __________.

    <p>======(________ )====== Multiple flagella on 2 poles</p> Signup and view all the answers

    Peritrichous means __________.

    <p>=====(_________)===== Flagella all over the bacterium</p> Signup and view all the answers

    What process secretes proteins across the inner and outer membrane in one step?

    <p>T1SS, T3SS, T4SS</p> Signup and view all the answers

    What does T3SS do?

    <p>Injects virulence factors directly into host cell</p> Signup and view all the answers

    What is a virulence factor for glycocalyx?

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

    Study Notes

    Bacterial Morphology

    • Coccus: Spherical shape of bacteria.
    • Bacillus: Rod-shaped bacteria.
    • Coccobacillus: Oval shape, intermediate between cocci and bacilli.
    • Diplococcus: Bacteria occurring in pairs of cocci.
    • Streptococcus: Bacteria arranged in chains of cocci.
    • Staphylococcus: Clusters of cocci bacteria.
    • Tetrad: Clusters of four cocci.

    Glycocalyx and Functions

    • Glycocalyx: Comprised of polysaccharides and glycoproteins, formed into a capsule or slime layer.
    • Functions:
      • Poorly antigenic.
      • Inhibits phagocytosis.
      • Promotes bacterial attachment.
      • Acts as a virulence factor in some bacterial species.

    Cell Wall Structure

    • Cell Wall: Semi-rigid structure made of cross-linked peptidoglycan, crucial for maintaining bacterial shape and preventing lysis.
    • Gram Staining:
      • Gram-positive: Retains violet stain; thick peptidoglycan layer (~25 layers).
      • Gram-negative: Retains pink counter stain; thin peptidoglycan layer (~2 layers).

    Gram-Negative Bacteria Structure

    • Periplasmic Space: Area between cytoplasmic membrane and outer membrane in Gram-negative bacteria, facilitates transport of proteins and enzymes.
    • Outer Membrane:
      • Bilayer with inner layer like cytoplasmic membrane and outer layer containing phospholipids and lipopolysaccharides (LPS), which serve as a protective barrier.
    • LPS Structure:
      • O Antigen: Antigenic component, composed of long carbohydrate units, highly variable among species.
      • Core Polysaccharide: Branched structure connecting O antigen to lipid A.
      • Lipid A: Embedded in outer membrane, acts as an endotoxin and is a virulence factor.

    Toxins

    • Exotoxins: Proteins secreted by living bacteria, contributing to virulence.
    • Endotoxins: Structural elements of lipopolysaccharide, specifically lipid A.

    Bacterial Virulence Factors

    • Teichoic and Lipoteichoic Acids: Found in Gram-positive bacteria, these act as virulence factors.
    • Flagella: Filamentous protein structures providing motility; source of H antigen.
    • Pili: Hair-like structures facilitating adherence and genetic material exchange (conjugation), also a virulence factor.
    • Endospores: Dormant, resistant forms produced by mainly Gram-positive bacteria in stress; examples include Bacillus anthracis and Clostridium tetani.
    • Virulence Factor for Glycocalyx: Functions in antiphagocytic properties.

    Antibiotics and Their Targets

    • Fosfomycin: Inhibits MurA, crucial in N-acetylglucosamine (NAG) synthesis.
    • D-Cycloserine: Interferes with addition of D-Alanine.
    • Daptomycin: Disrupts membrane polarization.
    • Oxacillin/Penicillins: Target transpeptidase for crosslinking in peptidoglycan.

    Flagella Arrangement

    • Monotrichous: Single flagellum at one pole.
    • Lophotrichous: Multiple flagella at one pole.
    • Amphitricous: Multiple flagella at both poles.
    • Peritrichous: Flagella distributed all around the bacterial surface.

    Protein Secretion Systems

    • Type 1, 3, and 4 Secretion Systems (T1SS, T3SS, T4SS): Mechanisms to secrete proteins across membranes in Gram-negative bacteria.
    • Type 3 Secretion System (T3SS): Injects virulence factors directly into host cells using a needle-like structure.

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    Description

    Explore the various shapes of bacteria, including cocci and bacilli, and their classifications. Understand the structure and functions of the glycocalyx and the importance of cell walls in bacterial survival. This quiz covers vital concepts in microbiology essential for students.

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