Chemotaxonomy: Microbial Cell Classification
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Questions and Answers

Where are respiratory quinones typically found in bacterial cells?

  • In the cell wall
  • In the outer membrane
  • In lipopolysaccharides
  • In the cytoplasmic membrane (correct)
  • What is the primary characteristic of respiratory quinones that makes them useful for chemotaxonomy?

  • Their ability to bind to fatty acids
  • The variation in the number of isoprene units and hydrogenated double bonds (correct)
  • Their presence in the outer membrane
  • Their ability to transport electrons
  • What type of fatty acids are commonly found in Gram-negative bacteria?

  • Hydroxyl-fatty acids
  • Cyclopropane fatty acids
  • Simple fatty acids with 8-20 carbon atoms (correct)
  • Iso- and anteiso- fatty acids
  • What is the characteristic of fatty acids that makes them useful for chemotaxonomy?

    <p>Their variation in carbon chain length and saturation</p> Signup and view all the answers

    Which of the following is NOT a type of respiratory quinone?

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

    In which type of bacteria are lipoteichoic acids typically found?

    <p>Gram-positive bacteria</p> Signup and view all the answers

    What is the main focus of chemotaxonomy?

    <p>The study of the chemical variation in microbial cells</p> Signup and view all the answers

    Which of the following is NOT a character used in bacterial chemotaxonomy?

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

    What is the significance of amino acid sequence in peptidoglycan?

    <p>It helps in identifying bacterial species</p> Signup and view all the answers

    What is the purpose of thin-layer chromatography in bacterial chemotaxonomy?

    <p>To separate whole cell sugars from whole cell hydrolysate</p> Signup and view all the answers

    What are the hydrophilic head groups of amphipathic polar lipids usually linked to?

    <p>Two hydrophobic fatty acid chains</p> Signup and view all the answers

    What is the most common type of polar lipids in bacterial plasma membranes?

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

    What is the significance of sugar composition in bacterial chemotaxonomy?

    <p>It provides characteristics for certain taxa</p> Signup and view all the answers

    What is the main component of bacterial plasma membranes?

    <p>Amphipathic polar lipids</p> Signup and view all the answers

    Study Notes

    Chemotaxonomy

    • Chemotaxonomy is the study of chemical variation in microbial cells and the use of chemical characteristics in the classification and identification of bacteria.
    • It examines the distribution of chemical macromolecules containing amino acids, peptides, lipids, polysaccharides, and other related polymers, proteins, enzymes, and complex polymeric molecules.

    Characters Used in Bacterial Chemotaxonomy

    • Peptidoglycan
    • Diamino acids
    • Polysaccharides
    • Teichoic acids
    • Mycolic acids
    • Fatty acids
    • Polar acids
    • Isoprenoid quinones
    • Polyamines
    • Prokaryotic pigments
    • LPS (Lipopolysaccharides)

    Amino Acids of the Cell Wall

    • Differences in amino acid sequence of peptide chains, mode of cross-links between chains, and diaminoacids present give important information for classification of bacteria.
    • Used for description of peptidoglycan type.

    Sugars of Whole Cell

    • Certain sugars are characteristic for certain taxa (family, genus, species).
    • Separation of whole cell sugars from whole cell hydrolysate by thin-layer chromatography:
      • Rha (rhamnose)
      • Xyl (xylose)
      • Man (mannose)
      • Rib (ribose)
      • Mad (madurose)
      • Ara (arabinose)
      • Glu (glucose)

    Polar Lipids

    • Important components of bacterial plasma membranes.
    • Amphipathic polar lipids consist of hydrophilic head groups linked to two hydrophobic fatty acid chains.
    • Phospholipids are the most common polar lipids, including:
      • Phosphatidyglycerol
      • Diphosphatidyglycerol
      • Phosphatidylcholine
      • Other phosphatidylglycolipids

    Respiratory Quinones

    • Constituents of bacterial cytoplasmic membrane and mitochondrial membrane.
    • Play an important role in the electron transport chain.
    • Chemotaxonomic value based on:
      • Different types of quinones (e.g., ubiquinones, menaquinones, and their derivatives)
      • Length of isoprenoid side chain
      • Number of saturated isoprenoid units

    Fatty Acids

    • Fatty acid profiles analysis is used for chemotaxonomy of bacteria.
    • Fatty acids are found in:
      • Cytoplasmic membrane
      • Lipopolysaccharides of outer membrane of Gram-negative bacteria
      • Lipoteichoic acids in Gram-positive bacteria
    • Characteristics of fatty acids:
      • Carbon chain length (8-20 carbon atoms)
      • Presence of saturated and unsaturated
      • Occurrence of methyl groups (iso-, anteiso-, and methylated)
      • Occurrence of cyclopropane fatty acid (cyclo 17:0, cyclo 19:0)
      • Occurrence of hydroxyl-fatty acid with an OH-group at position 2 or 3 of the molecule

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    Learn about chemotaxonomy, the study of chemical variations in microbial cells, and how it's used to classify and identify bacteria. Explore the distribution of chemical macromolecules and their role in identification.

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