Microbiology 101: Types of Microbes
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Questions and Answers

What is the minimum number of subunits in an icosahedral capsid?

  • 120
  • 60 (correct)
  • 30
  • 90

    • Which of the following viral symmetries is characterized by a continuous cylinder surrounded by a lipid layer and complex proteinaceous core wall?

  • Complex (correct)
  • Icosahedral
  • Helical
  • Oblong

    • What is the function of the viral matrix protein in the viral envelope?

  • To determine the tropism of the virus
  • To mediate the interaction between the capsid and envelope (correct)
  • To attach to membrane proteins in the host cell
  • To transcribe the viral genome

    • Which of the following statements is true about enveloped viruses?

    <p>They often survive only transiently outside the host</p> Signup and view all the answers

    What is the term for the repeating units of protein that make up the helical capsid?

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

    Which of the following viruses has an icosahedral capsid?

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

    What is the term for the viral genome enclosed by the capsid protein coat?

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

    What is the function of the HA protein in the influenza virion?

    <p>To attach to membrane proteins in the host cell</p> Signup and view all the answers

    Which bacterial structure is responsible for attachment and conjugation?

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

    Which of the following is NOT a characteristic of Gram-positive bacteria?

    <p>Presence of lipopolysaccharide (LPS)</p> Signup and view all the answers

    What is the primary function of the capsule in bacteria?

    <p>Resistance to phagocytosis</p> Signup and view all the answers

    Which staining technique is used to visualize Mycobacterium tuberculosis?

    <p>Ziehl-Neelsen (ZN) stain</p> Signup and view all the answers

    What is the primary role of plasmids in bacteria?

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

    Which of the following bacteria cannot be visualized with the Gram stain?

    <p>Mycobacterium tuberculosis</p> Signup and view all the answers

    What is the main component of the bacterial capsule?

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

    Which of the following statements about spores is TRUE?

    <p>They are highly resistant to heat, chemicals, and drying.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of Gram-negative bacteria?

    <p>Presence of teichoic acids</p> Signup and view all the answers

    What is the function of the mordant in the Gram stain?

    <p>Fix the dye to the bacterial cell wall</p> Signup and view all the answers

    What is the primary function of viral mRNA?

    <p>To express the viral proteins</p> Signup and view all the answers

    Which type of virus encodes many of the enzymes they need, such as DNA-dependent RNA polymerase?

    <p>Large viruses, e.g., pox-, herpes-</p> Signup and view all the answers

    What is a critical step in the viral replication process that involves the use of host cell machinery?

    <p>Translation of viral proteins</p> Signup and view all the answers

    What is the primary difference between large and small viruses in terms of gene expression and replication?

    <p>Small viruses use host cell enzymes, while large viruses encode their own enzymes</p> Signup and view all the answers

    What is the role of the viral genome structure in determining the route to produce viral mRNA?

    <p>It determines the route to produce viral mRNA</p> Signup and view all the answers

    What is the correct sequence of gene expression and replication?

    <p>DNA, mRNA, protein</p> Signup and view all the answers

    Which type of virus has a genome structure that involves the use of host or viral RNA polymerase to produce mRNA?

    <p>All of the above</p> Signup and view all the answers

    What is the correct description of the attachment step in viral replication?

    <p>The process by which the virus attaches to the host cell surface</p> Signup and view all the answers

    What is a key distinguishing characteristic of viruses compared to bacteria and fungi?

    <p>Require host cell machinery for replication</p> Signup and view all the answers

    Which group of microbes is characterized by having eukaryotic cells?

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

    What is the typical generation time for macroparasites compared to microparasites?

    <p>Relatively long for macroparasites and short for microparasites</p> Signup and view all the answers

    What is the primary role of RNA-dependent RNA polymerase in RNA genomes?

    <p>To synthesize RNA using complementary RNA as template</p> Signup and view all the answers

    How are organisms classified in taxonomy?

    <p>Based on similar characteristics into related groups</p> Signup and view all the answers

    Which of the following accurately describes prions?

    <p>Protein-based infectious agents without nucleic acids</p> Signup and view all the answers

    In the context of retroviruses, what enzyme is responsible for converting +ve ssRNA into dsDNA?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What characteristic is unique to bacteria in comparison to viruses and fungi?

    <p>Reproductive method of binary fission</p> Signup and view all the answers

    What characteristic distinguishes prion diseases from other infectious diseases?

    <p>They are caused by misfolded proteins</p> Signup and view all the answers

    Which microbial group has a flexible outer membrane?

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

    Which of the following is a common symptom of toxoplasmosis in most cases?

    <p>No symptoms typically</p> Signup and view all the answers

    Which of the following statements is true regarding ribosomes in different groups of microbes?

    <p>Fungi have 80S ribosomes</p> Signup and view all the answers

    What type of organism is Taenia solium, which is mentioned along with prion diseases?

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

    How do macroparasites typically reproduce compared to microparasites?

    <p>They replicate outside the host releasing eggs or larvae</p> Signup and view all the answers

    Leishmaniasis primarily manifests in which form?

    <p>Cutaneous ulcers</p> Signup and view all the answers

    Which of the following correctly identifies the cellular structure of bacteria?

    <p>Prokaryotic cells with rigid cell walls</p> Signup and view all the answers

    Study Notes

    Microbial Classification

    • Organisms that cause infectious diseases can be grouped into:
      • Parasites: Helminths and Protozoa
      • Fungi
      • Bacteria
      • Viruses
      • Prions
    • Each group has distinctive characteristics that determine how they interact with hosts and cause disease, including:
      • Structural and molecular make-up
      • Biochemical and metabolic strategies
      • Reproductive processes

    Comparison of Microbes

    • Characteristics of microbes:
      • Viruses:
        • No cells
        • DNA or RNA
        • No nucleus
        • No ribosomes
        • No membrane-bound organelles
        • Protein capsid
        • Require host cell machinery for replication
      • Bacteria:
        • Cells
        • DNA and RNA
        • Prokaryotic nucleus
        • 70S ribosomes
        • No membrane-bound organelles
        • Rigid cell wall containing peptidoglycan
        • Binary fission replication
      • Fungi:
        • Cells
        • DNA and RNA
        • Eukaryotic nucleus
        • 80S ribosomes
        • Membrane-bound organelles
        • Rigid cell wall containing chitin
        • Budding or mitosis replication
      • Protozoa and Helminths:
        • Cells
        • DNA and RNA
        • Eukaryotic nucleus
        • 80S ribosomes
        • Membrane-bound organelles
        • Flexible membrane
        • Mitosis replication

    Macroparasites vs Microparasites

    • Characteristics of macroparasites and microparasites:
      • Macroparasites:
        • Big (naked eye)
        • Replicate outside host
        • Long generation time
        • Weak and short-lived immunity
      • Microparasites:
        • Small (microscope)
        • Replicate within host
        • Short generation time
        • Immunity present

    Structure of Bacteria

    • Cell wall:
      • Gram-positive cell wall: thick peptidoglycan layer, no outer membrane, low lipid and lipoprotein content, teichoic and lipoteichoic acids present
      • Gram-negative cell wall: thin peptidoglycan layer, outer membrane present, high lipid and lipoprotein content, lipopolysaccharide present
    • Other components:
      • Capsule: gelatinous layer outside cell wall, composed of polysaccharides, determinant of virulence, used for identification and lab diagnosis
      • Flagella: organ of motility, fixed number and location, plays a role in pathogenesis, used for identification and lab diagnosis
      • Pili (fimbriae): hair-like filaments, attachment and conjugation functions
      • Plasmids: extra-chromosomal genetic material, capable of self-replication, can contain antibiotic resistance genes
      • Spores: highly resistant structures formed in response to adverse conditions, contain bacterial DNA surrounded by a thick keratin-like coat

    Structure of Viruses

    • Components:
      • Capsid: protein coat that surrounds the viral genome
      • Genome: viral genetic material, can be DNA or RNA
      • Envelope: lipid bilayer derived from the host cell membrane, contains viral glycoproteins
    • Types of symmetry:
      • Icosahedral: 20 solid equilateral triangles arranged around the face of a sphere
      • Helical: capsomeres bound in a periodic fashion to the viral genome
      • Complex: neither purely helical nor purely icosahedral
    • Importance of viral surface proteins:
      • Attach to membrane proteins (receptors) in host cell, determinants of tropism
      • Targets for antibodies, determinants of antibody specificity (serotype)

    Basic Steps of Viral Replication

    • Attachment
    • Entry
    • Uncoating
    • Production of viral proteins and replication of viral genome
    • Assembly
    • Release

    Gene Expression and Replication

    • The principle: transcription and translation
    • The fact: viral protein synthesis is completely dependent on cellular translation machinery
    • Route to produce viral mRNA depends on genome structure of each virus
    • Examples:
      • DNA genomes: large viruses encode many of the enzymes they need, small viruses use host cell enzymes
      • RNA genomes: most examples encode their own RNA-dependent RNA polymerase
      • Retroviruses: use reverse transcriptase to copy a +ve ssRNA genome into dsDNA

    Prion Diseases

    • Group of fatal and infectious neurodegenerative diseases
    • Infectious agent propagates in the absence of nucleic acid
    • Infectious agent is a misfolded protein that alters folding of the normal host version of the protein

    Parasites

    • Examples:
      • Taenia solium (pork tapeworm)
      • Schistosomiasis
      • Malaria
      • Toxoplasmosis
      • Leishmaniasis

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    Description

    Learn about the classification of microbes and the characteristics that distinguish them. From parasites to viruses, understand how these microorganisms interact with their hosts and cause disease.

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