Biology of Microbial Cells Lecture 1
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Questions and Answers

What is the study of very small living organisms called?

  • Microbiology (correct)
  • Pathology
  • Micrology
  • Biology

    • What percentage of known microbes are pathogenic?

  • 20%
  • 3% (correct)
  • 5%
  • 10%

    • Who is credited with disproving spontaneous generation?

  • Charles Darwin
  • Louis Pasteur (correct)
  • Antony Van Leeuwenhock
  • Gregor Mendel

    • What is the term for the microorganisms that live within and on humans?

    <p>Indigenous microbiota</p> Signup and view all the answers

    What is the term for the theory that diseases are caused by microorganisms?

    <p>Germ theory of disease</p> Signup and view all the answers

    What is the term for the process of preventing the growth of microorganisms?

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

    What is the function of lysozyme in animal secretions?

    <p>To function as a major line of defense against bacterial infection</p> Signup and view all the answers

    What is the main component of the cell wall in gram-positive bacteria?

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

    What is the purpose of teichoic acids in gram-positive bacteria?

    <p>To bind Ca2+ and Mg2+ for eventual transport into the cell</p> Signup and view all the answers

    What is the main component of the cell wall in gram-negative bacteria?

    <p>Outer membrane</p> Signup and view all the answers

    What is the term for the toxic component of LPS?

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

    What is the pathogenicity of gram-negative bacteria due to?

    <p>Their toxic outer membrane</p> Signup and view all the answers

    What is the function of Lipid A in LPS?

    <p>To induce an immune response in the host</p> Signup and view all the answers

    What is the composition of the outer membrane in gram-negative bacteria?

    <p>Lipid and polysaccharide linked together</p> Signup and view all the answers

    What is the primary contribution of Robert Koch in the field of microbiology?

    <p>Development of pure culture techniques</p> Signup and view all the answers

    What is the main purpose of Koch's Postulates?

    <p>To show that a specific organism causes a specific disease</p> Signup and view all the answers

    Who is credited with the discovery and description of endospores?

    <p>Ferdinand Cohn</p> Signup and view all the answers

    What is the focus of Environmental Microbiology?

    <p>Pollution of soil, air, and water and biodegradation of toxic chemicals</p> Signup and view all the answers

    What is the term introduced to mean the complete removal of all life forms including endospores?

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

    What is the focus of Agricultural Microbiology?

    <p>Microorganisms as biofertilizers and biocontrol agents of plant pathogens</p> Signup and view all the answers

    What is the field of biology that provides scientific names for organisms and describes them?

    <p>Systematic biology</p> Signup and view all the answers

    What was the original classification system developed by Aristotle?

    <p>Two kingdoms: plants and animals</p> Signup and view all the answers

    What is the primary function of porins in the outer membrane of bacteria?

    <p>To act as channels for the entrance and exit of hydrophilic low-molecular-weight substances</p> Signup and view all the answers

    What is the main difference between the cell walls of gram-positive and gram-negative bacteria?

    <p>The thickness of the cell walls, with gram-positive bacteria having thicker walls</p> Signup and view all the answers

    What happens to the insoluble crystal violet-iodine complex during the Gram stain reaction in gram-positive bacteria?

    <p>It is retained by the cell due to the thick peptidoglycan layer</p> Signup and view all the answers

    What is the purpose of the outer membrane in gram-negative bacteria?

    <p>To keep proteins from diffusing away from the cell</p> Signup and view all the answers

    What is the characteristic of the periplasm contents?

    <p>They are highly concentrated</p> Signup and view all the answers

    What is the location of the periplasm?

    <p>Between the outer surface of the cytoplasmic membrane and the inner surface of the outer membrane</p> Signup and view all the answers

    What is the approximate width of the periplasm?

    <p>15 nm</p> Signup and view all the answers

    Why are gram-negative bacteria nearly invisible after alcohol treatment in the Gram stain?

    <p>The alcohol extracts the crystal violet-iodine complex from the cell</p> Signup and view all the answers

    What is the main function of the cell membrane in bacterial cells?

    <p>To facilitate the active transport of nutrients into the cell</p> Signup and view all the answers

    What is the main component of the bacterial cell wall?

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

    What is the function of the enzyme lysozyme in relation to the bacterial cell wall?

    <p>To break the β-1,4-glycosidic bonds in peptidoglycan</p> Signup and view all the answers

    What is the result of the destruction of peptidoglycan in the bacterial cell wall?

    <p>Water enters the cell and the cell swells and eventually bursts</p> Signup and view all the answers

    What is the function of the cell wall in bacterial cells?

    <p>To protect the interior structure of the cell from adverse changes in the outside environment</p> Signup and view all the answers

    What is the role of peptidoglycan in the bacterial cell wall?

    <p>To form a mesh-like layer outside the cell membrane</p> Signup and view all the answers

    What is the composition of the sugar component of peptidoglycan?

    <p>Alternating residues of β-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid</p> Signup and view all the answers

    What is the significance of the cell wall in bacterial cells?

    <p>It prevents bacterial cells from rupturing due to osmotic pressure</p> Signup and view all the answers

    Study Notes

    Biology of Microbial Cell

    • Microbiology is the study of very small living organisms, known as microorganisms or microbes, which require a microscope to be seen.
    • Microorganisms include bacteria, algae, protozoa, fungi, and viruses, with only 3% of them being pathogenic (disease-causing).

    History of Microbiology

    • The concept of microorganisms was first suggested by Antony Van Leeuwenhock, who discovered "animalcules".
    • The Golden Age of Microbiology was marked by Louis Pasteur's work, which showed that microbes caused fermentation and spoilage, and disproved spontaneous generation.
    • Pasteur also developed aseptic techniques, which involved removing pathogenic microorganisms from the environment.

    Microbiology and Medicine

    • The Germ Theory of Disease states that diseases are transmitted by microorganisms from a diseased person to a healthy person.
    • Examples of diseases caused by specific microorganisms include Diphtheria (Corynebacterium diphtheriae) and Tetanus (Clostridium tetani).
    • Robert Koch developed solid growth media, pure culture techniques, and aseptic lab techniques, and isolated bacteria as causative agents for Anthrax.

    Koch's Postulates

    • Koch's Postulates are a series of experimental steps to show that a specific organism causes a specific disease.

    Spores and Sterilization

    • Ferdinand Cohn discovered and described endospores, and the term "sterile" was introduced to mean the complete removal of all life forms, including endospores.

    Microbiology Branches

    • Basic Microbiology: classifications, metabolism, nutrition, growth, and requirements.
    • Medical Microbiology: human pathogens.
    • Industrial Microbiology: microorganisms used to obtain industrial products.
    • Pharmaceutical Microbiology: production of drugs, enzymes, and solvents using microorganisms.
    • Agricultural Microbiology: microorganisms used as biofertilizers and biocontrol agents of plant pathogens.
    • Environmental Microbiology: microbial ecology, pollution, and biodegradation of toxic chemicals.

    Classification

    • Systematic biology provides scientific names, descriptions, and classifications for organisms.
    • Aristotle divided the living world into two kingdoms: plants and animals, which persisted for over 2000 years.
    • By the 19th century, a third kingdom, Protista, was added to accommodate microorganisms.

    Cell Wall of Bacteria

    • The cell wall is responsible for the shape of the cell, protects the interior structure, and prevents bacterial cells from rupturing due to osmotic pressure.
    • The cell wall is composed of peptidoglycan, a polymer consisting of sugars and amino acids.
    • Peptidoglycan can be destroyed by agents such as lysozyme, an enzyme that breaks the β-1,4-glycosidic bonds between N-acetylglucosamine and N-acetylmuramic acid.

    Gram-Positive and Gram-Negative Cell Walls

    • Gram-positive bacteria have a thick cell wall consisting of several layers of peptidoglycan, with teichoic acids embedded in the cell wall.
    • Gram-negative bacteria have a thin cell wall consisting of peptidoglycan, with a lipopolysaccharide layer (LPS) in the outer membrane.
    • LPS is composed of polysaccharide, lipid A, and O-polysaccharide (O antigen), and is responsible for the pathogenicity of Gram-negative bacteria.

    Periplasm

    • The periplasm is a region between the outer surface of the cytoplasmic membrane and the inner surface of the outer membrane, about 15 nm wide.
    • The periplasm contains proteins that are present outside the cytoplasmic membrane, but are kept from diffusing away by the outer membrane.

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    Description

    This quiz covers the basics of microbiology, including the definition of biology and microbiology, types of microorganisms, and the role of microorganisms in disease and health.

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