Introduction to Medical Microbiology
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Questions and Answers

What characterizes prokaryotic cells compared to eukaryotic cells?

  • DNA in the form of a single circular chromosome (correct)
  • Several chromosomes within a nucleus
  • Presence of a distinct nucleus
  • Membership in multicellular organisms

    • Which of the following types of microorganisms is NOT considered to cause infectious diseases?

  • Bacteria
  • Fungi
  • Prions
  • Amino acids (correct)

    • In which cellular structure does transcription occur in eukaryotic cells?

  • Ribosomes
  • Nucleus (correct)
  • Plasmids
  • Cytoplasm

    • What type of DNA is carried in plasmids within prokaryotic cells?

    <p>Extra-chromosomal DNA</p> Signup and view all the answers

    Which of these structures is typically absent in prokaryotic cells?

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

    What is the primary role of ribosomes in cells?

    <p>Site of protein synthesis</p> Signup and view all the answers

    Which of the following statements distinguishes bacterial cells from eukaryotic cells?

    <p>Bacteria can perform transcription and translation simultaneously</p> Signup and view all the answers

    Which of the following is a key difference between prokaryotic and eukaryotic cells regarding their organelles?

    <p>Eukaryotes contain membrane-bound organelles</p> Signup and view all the answers

    What is the primary method of reproduction for bacteria?

    <p>Binary fission</p> Signup and view all the answers

    Which type of bacteria has a thick peptidoglycan layer in its cell wall?

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

    What temperature and method are effective for inactivating bacteria through autoclaving?

    <p>120°C under pressure</p> Signup and view all the answers

    What unique feature do Mycobacterium have in their cell walls?

    <p>Large amounts of mycolic acids</p> Signup and view all the answers

    Which of the following bacteria are classified as gram-negative?

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

    What characteristic makes Gram staining unreliable for certain bacteria?

    <p>Starved or stationary-phase cultures</p> Signup and view all the answers

    Which group of pathogenic bacteria invade eukaryotic cells from outside and do not penetrate them?

    <p>Extracellular bacteria</p> Signup and view all the answers

    Which type of bacteria lacks a cell wall?

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

    What characteristic defines obligate intracellular bacteria?

    <p>They cannot live outside of host cells.</p> Signup and view all the answers

    Which of the following bacteria is classified as an extracellular pathogen?

    <p>Escherichia coli</p> Signup and view all the answers

    Why were Chlamydiae previously thought to be viruses?

    <p>They are obligate intracellular parasites.</p> Signup and view all the answers

    Which bacteria can be categorized as spherical in shape?

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

    Which of the following best describes diplococci?

    <p>Cocci arranged in pairs</p> Signup and view all the answers

    Obligate intracellular bacteria require what for growth?

    <p>A cell culture or living host.</p> Signup and view all the answers

    Which of these statements about obligate intracellular bacteria is false?

    <p>They can be cultured on standard laboratory media.</p> Signup and view all the answers

    What is NOT a typical shape of bacteria?

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

    What characteristic distinguishes fastidious bacteria from non-fastidious bacteria?

    <p>Fastidious bacteria require special nutritional supplements to grow.</p> Signup and view all the answers

    Which genera are known to include spore-forming bacteria?

    <p>Bacillus and Clostridium</p> Signup and view all the answers

    How do aerotolerant anaerobes react to exposure to oxygen?

    <p>They are not killed but do not prefer oxygen.</p> Signup and view all the answers

    What is the purpose of developing a universal phylogenetic tree for bacteria?

    <p>To understand evolutionary relationships based on RNA sequences.</p> Signup and view all the answers

    Which statement regarding spore formation in bacteria is true?

    <p>Spore formation provides resistance to harsh environments.</p> Signup and view all the answers

    What structure is formed when cocci divide in three planes?

    <p>Cubical packets</p> Signup and view all the answers

    Which group of bacteria has an absolute requirement for oxygen to grow?

    <p>Obligate aerobes</p> Signup and view all the answers

    What is a characteristic of facultative anaerobes?

    <p>They grow preferentially using oxygen but can survive without it.</p> Signup and view all the answers

    Which type of bacteria are usually harmed or killed by the presence of oxygen?

    <p>Obligate anaerobes</p> Signup and view all the answers

    What type of bacterial arrangement is characterized by cells adhering after repeated divisions in one plane?

    <p>Long chains</p> Signup and view all the answers

    Which of the following statements about aerobes is correct?

    <p>Aerobes require molecular oxygen for survival and growth.</p> Signup and view all the answers

    What is the defining feature of anaerobes?

    <p>They cannot grow in the presence of oxygen.</p> Signup and view all the answers

    What type of bacteria typically grows in grape-like clusters?

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

    Study Notes

    Introduction to Medical Microbiology

    • Medical microbiology focuses on preventing, diagnosing, and treating infectious diseases caused by microorganisms such as bacteria, fungi, parasites, viruses, and prions.
    • All living organisms are composed of either prokaryotic or eukaryotic cells, distinguished by their cellular organization and biochemistry.

    Prokaryotic vs Eukaryotic Cells

    • Prokaryotic cells lack a distinct nucleus, contain a single circular chromosome, possess additional DNA in plasmids, and can carry out transcription and translation simultaneously.
    • Eukaryotic cells contain DNA on multiple chromosomes within a nucleus, have a nuclear membrane, and separate transcription from translation.
    • Eukaryotes contain membrane-bound organelles (mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes) absent in prokaryotes.

    Bacteria: Prokaryotic Cells

    • Bacteria are single-celled prokaryotes, measuring between 0.1 to 10.0 μm.
    • Bacteria reproduce through binary fission.
    • Bacteria contain free DNA within the cytoplasm, energy-producing systems, and biosynthetic machinery necessary for growth and reproduction.
    • Bacteria can be inactivated by boiling, autoclaving at 120°C under pressure, or hot air oven treatment at 170°C.

    Bacterial Classification

    • Bacteria can be classified by:
      • Cell wall structure: Gram-positive bacteria have a thick peptidoglycan layer (e.g., Staphylococcus, Streptococcus, Clostridium, Bacillus), while gram-negative bacteria have a thin peptidoglycan layer and outer membrane (e.g., Enteric rods like Escherichia, Shigella, Salmonella, Enterobacter).
      • Mycobacteria: They contain mycolic acids within their cell walls, making them resistant to typical Gram staining.
      • Mycoplasma: These bacteria lack a cell wall.
      • Intracellular/Extracellular Invasion:
        • Extracellular Bacteria: They do not invade cells and proliferate in the extracellular environment (e.g., Vibrio cholera, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes).
        • Obligate Intracellular Bacteria: They cannot survive outside host cells and rely on host cells for energy and biosynthesis (e.g., Chlamydial cells). They cannot be grown in laboratory media and require viable eukaryotic cells.

    Cell Morphology: Shape and Arrangement

    • Shape: Bacteria can be categorized based on their shape:
      • Coccus: Spherical bacteria
      • Bacillus: Rod-shaped bacteria
      • Spiral: Spiral-shaped bacteria
      • Filamentous: Filamentous bacteria
    • Arrangement:
      • Diplococci: Cocci arranged in pairs.
      • Streptococcus and Enterococcus: Cocci arranged in long chains.
      • Staphylococci: Cocci arranged in grape-like clusters.
      • Tetrads: Cocci arranged in square groups of four.
      • Sarcina: Cocci arranged in cubical packets of eight.

    Growth Characteristics

    • Oxygen Requirement:
      • Aerobes: Grow in ambient air, requiring oxygen as a terminal electron acceptor.
      • Obligate Aerobes: Absolutely require oxygen for growth.
      • Anaerobes: Cannot grow in the presence of oxygen.
      • Obligate Anaerobes: Grow only under anaerobic conditions and are sensitive to oxygen.
      • Facultative Anaerobes: Can grow under both aerobic and anaerobic conditions, preferring oxygen.
      • Aerotolerant Anaerobes: Are anaerobic bacteria that are not killed by exposure to oxygen.
    • Spore Formation:
      • Certain bacteria (e.g., Bacillus and Clostridium) form spores, durable coats of protein allowing survival under extreme conditions.
    • Fastidious/Non-fastidious:
      • Fastidious bacteria: Require special nutritional supplements and conditions for growth.
      • Non-fastidious bacteria: Do not require special nutritional supplements or conditions.

    Phylogenetic Tree: 16s rRNA Sequencing

    • Phylogenetic classification relies on comparing 16s ribosomal RNA sequences. These sequences are highly conserved and change slowly, allowing for a universal phylogenetic tree of bacteria.

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    Description

    This quiz explores the fundamentals of medical microbiology, focusing on the differences between prokaryotic and eukaryotic cells. It covers the characteristics of microorganisms such as bacteria, fungi, and viruses. Test your knowledge on the prevention, diagnosis, and treatment of infectious diseases caused by these pathogens.

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