Introduction to Microbiology
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Questions and Answers

Which branch of microbiology focuses specifically on the study of microorganisms that can cause diseases in humans?

  • Microbial taxonomy
  • Genetic engineering
  • Medical microbiology (correct)
  • Biotechnology

    • What do the domains Bacteria and Archaea have in common?

  • Both contain peptidoglycan in their cell walls.
  • Both are known for their complex multicellular structures.
  • Both have eukaryotic cell types.
  • Both are unicellular and prokaryotic. (correct)

    • Which component is found in the cell walls of bacteria that contributes to their rigidity?

  • Lipid bilayer
  • Peptidoglycan (correct)
  • Chitin
  • Cellulose

    • In which field does the study of fungi, including yeasts and molds, belong?

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

    What is the focus of immunology within the branches of microbiology?

    <p>Systems of body defenses against infection</p> Signup and view all the answers

    Which of the following best describes the cellular structure of Eukarya?

    <p>Eukaryotic with complex multicellular forms</p> Signup and view all the answers

    How are bacteria ecologically diverse?

    <p>Some bacteria can photosynthesize, while others cannot.</p> Signup and view all the answers

    What role does biotechnology play in microbiology?

    <p>Use of organisms to produce desired products</p> Signup and view all the answers

    What is the correct order of bacterial taxonomy from highest to lowest rank?

    <p>Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species</p> Signup and view all the answers

    Which statement is true regarding binomial nomenclature?

    <p>The genus name can be used alone, but not the species name.</p> Signup and view all the answers

    What kind of bacterial arrangement is characterized by cocci occurring in chains?

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

    Which of the following is NOT a characteristic shape classification of bacteria?

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

    Which bacterium is recognized as the smallest capable of existing outside a host?

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

    What is the primary component of the bacterial cell wall?

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

    What shape are bacilli bacteria?

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

    What type of bacteria are described as having a rigid cell wall affecting their shape?

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

    Which feature is commonly found in gram-positive bacteria but absent in gram-negative bacteria?

    <p>Teichoic acids</p> Signup and view all the answers

    What is one of the key functions of a bacterial capsule?

    <p>To limit phagocytosis by immune cells</p> Signup and view all the answers

    What is a defining feature of pleomorphic bacteria?

    <p>They can change shapes.</p> Signup and view all the answers

    Which of the following accurately describes the difference in cell wall thickness between gram-positive and gram-negative bacteria?

    <p>Gram-positive walls have a thicker peptidoglycan layer</p> Signup and view all the answers

    How are bacterial species examples typically represented in nomenclature?

    <p>Genus name capitalized, species name lowercase</p> Signup and view all the answers

    What type of bacterial appendage is primarily responsible for motility?

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

    Which of the following arrangements of cocci is NOT possible?

    <p>In a single line</p> Signup and view all the answers

    Which of the following components is NOT present in the cell envelope of prokaryotic cells?

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

    What are capsules in bacteria primarily composed of?

    <p>Complex polysaccharides and polypeptides</p> Signup and view all the answers

    The space that exists between the outer membrane and the cytoplasmic membrane in gram-negative bacteria is known as what?

    <p>Periplasmic space</p> Signup and view all the answers

    How do the sugar components of the polysaccharide capsule influence bacterial classification?

    <p>They differentiate the serologic types within a species.</p> Signup and view all the answers

    What is the composition of the glycocalyx in bacteria?

    <p>A polysaccharide coating that is loosely attached</p> Signup and view all the answers

    What is a unique feature of bacterial ribosomes compared to eukaryotic ribosomes?

    <p>Bacterial ribosomes have a 70S size.</p> Signup and view all the answers

    Which of the following statements correctly describes the slime layer?

    <p>It is a loosely attached layer aiding in adherence to surfaces.</p> Signup and view all the answers

    What role does the glycocalyx play in biofilms?

    <p>It helps bacteria adhere firmly to various structures.</p> Signup and view all the answers

    Which of the following does NOT characterize the cytoplasm in bacteria?

    <p>It is exclusively liquid without any structures.</p> Signup and view all the answers

    What component of the cell wall is present only in bacterial cells and targets antibacterial drugs?

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

    Which bacteria are characterized by their resistance to Gram staining?

    <p>Acid-fast bacteria</p> Signup and view all the answers

    What is the role of porin proteins in bacterial cell walls?

    <p>To facilitate the transport of small molecules</p> Signup and view all the answers

    Which of the following statements about protoplasts is true?

    <p>They are sensitive to osmolarity.</p> Signup and view all the answers

    The lipopolysaccharides found in the cell walls of gram-negative bacteria serve what function?

    <p>Function as endotoxins</p> Signup and view all the answers

    What is the primary component that gives Mycobacteria their acid-fast property?

    <p>Mycolic acids</p> Signup and view all the answers

    Which of the following best describes teichoic acid in the context of bacterial cell walls?

    <p>An antigen that aids in laboratory identification</p> Signup and view all the answers

    What term is used to describe a bacterial cell that is devoid of its cell wall?

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

    What are bacteriocins primarily known for?

    <p>Being toxic proteins lethal to other bacteria</p> Signup and view all the answers

    Which type of transposition involves the movement of DNA without replication?

    <p>Direct transposition</p> Signup and view all the answers

    Which category of flagella describes bacteria with flagella distributed all over their surface?

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

    Pili are primarily used for what function in bacteria?

    <p>Attachment to surfaces</p> Signup and view all the answers

    What characteristic distinguishes monotrichous bacteria from other types?

    <p>A single polar flagellum</p> Signup and view all the answers

    Which statement regarding plasmids and transposons is correct?

    <p>Plasmids are capable of independent replication, while transposons cannot.</p> Signup and view all the answers

    What type of movement do spirochetes use for locomotion?

    <p>Axial filament structure</p> Signup and view all the answers

    Which of the following is NOT a classification of flagellar arrangement?

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

    Study Notes

    Introduction to Microbiology

    • Medical microbiology is the study of microorganisms (bacteria, viruses, fungi, and parasites) that cause diseases in humans
    • It includes pathogenesis, disease pathology, immunology, and epidemiology of diseases

    Branches of Microbiology

    • Bacteriology: The study of bacteria (the smallest, simplest single-celled organisms)
    • Mycology: The study of fungi (including microscopic forms—molds and yeasts—and larger forms—mushrooms)
    • Parasitology: The study of parasites (including pathogenic protozoa and helminths)
    • Virology: The study of viruses (minute particles that parasitize living things)
    • Immunology: The study of the immune systems that protect against infection
    • Microbial taxonomy: The classification, naming, and identification of microorganisms
    • Biotechnology: Any process in which humans use the systems or processes of organisms to create a desired product

    Genetic engineering and recombinant DNA technology

    • Techniques that alter the genetic makeup of organisms to introduce new compounds, different genetic combinations, and/or unique organisms.

    The Universal Tree of Life

    • Based on ribosomal RNA (rRNA) analysis, life is divided into three domains: Archaea, Bacteria, and Eukarya
    • Bacteria and Archaea are prokaryotic but not closely related
    • Eukarya includes protists, fungi, plants, and animals

    Members of the domain Bacteria

    • Unicellular and prokaryotic
    • Thick, rigid cell walls surrounding a cell membrane containing peptidoglycan
    • Diverse ecologically (free-living soil organisms to deadly parasites); some photosynthesize, others require oxygen, and still others are killed by oxygen

    Ranks or Levels of Bacterial Taxonomy (descending order)

    • Domain: Collection of similar kingdoms
    • Kingdom: Collection of similar phyla or divisions
    • Phylum/Division: Collection of similar classes
    • Classes: Collection of similar orders
    • Orders: Collection of similar families
    • Families: Collection of similar genera
    • Genera: Collection of related species
    • Species: Group of related isolates or strains

    Binomial Nomenclature

    • Organisms are named using binomial nomenclature (e.g., Escherichia coli)
    • Genus name comes first, is capitalized, and italicized or underlined
    • Species name comes second, is not capitalized, and italicized or underlined
    • The genus name may be used alone; the species name cannot

    Bacterial Morphology

    • Bacteria are classified by shape: cocci (round), bacilli (rods), and spirochetes (spiral)
    • Bacteria can be pleomorphic (variable in shape)
    • Arrangement (e.g., clusters, chains) is important for identification

    Structure of Bacteria

    • Prokaryotic cells have three architectural regions: cell envelope (capsule, cell wall, plasma membrane), cytoplasmic region (DNA, ribosomes, inclusions), and appendages (flagella, pili)
    • The cell wall, composed of peptidoglycan (except in Mycoplasma), is the outermost component.
    • Mycoplasma have no cell wall

    Cell Walls of Gram-Positive and Gram-Negative Bacteria

    • Gram-positive bacteria have a thicker peptidoglycan layer and teichoic acids
    • Gram-negative bacteria have a complex outer layer (lipopolysaccharide, lipoprotein, phospholipid). The outer membrane contains endotoxin (lipopolysaccharide)
    • The periplasmic space between the outer and cytoplasmic membrane is in gram-negative bacteria

    Cell Walls of Acid-Fast Bacteria

    • Mycobacteria have an unusual cell wall with high lipid content, making them acid-fast
    • Acid-fast bacteria resist decolorization with acid-alcohol after staining with carbolfuchsin

    Peptidoglycan

    • Found in bacterial cell walls; provides structural support. Synonyms include murein and mucopeptide.
    • Target for antibacterial drugs (e.g., penicillins, cephalosporins, vancomycin)

    Lipopolysaccharide (LPS)

    • Component of the outer membrane of gram-negative bacteria; is endotoxin

    Teichoic Acid

    • Found in gram-positive bacteria, part of the cell wall
    • Causes septic shock

    Cytoplasmic Membrane

    • Phospholipid bilayer
    • Important for active transport, energy generation, cell wall synthesis, and secretion of enzymes/toxins
    • sterols are absent, except in Mycoplasma.

    Capsule

    • Organized layer of glycocalyx
    • Attached to the cell wall; comprised of polysaccharide or polypeptide
    • Important for adherence, resistance to phagocytosis, and infection

    Slime Layer

    • Unorganized layer surrounding bacterial cell
    • Polysaccharide coating aiding adherence and biofilm formation

    Ribosomes

    • Site of protein synthesis
    • Bacterial ribosomes (70S) differ in size and composition from eukaryotic ribosomes (80S)
    • Target for some antibiotics

    Granules

    • Cytoplasmic storage areas for nutrients

    Nucleoid

    • Region of the cytoplasm where bacterial DNA is located; single, circular molecule

    Plasmids

    • Small, circular DNA molecules replicating independently of the chromosome
    • Carry genes for antibiotic resistance, heavy metal resistance, UV light resistance, pili formation, toxins
    • Transmissible vs. non-transmissible plasmids

    Transposons

    • Pieces of DNA that can move from one site to another (jumping genes)

    Flagella

    • Long, whiplike appendages for chemotaxis (movement toward nutrients)
    • Different arrangements (e.g., monotrichous, lophotrichous, amphitrichous, peritrichous, atrichous)

    Pili (Fimbriae)

    • Hairlike filaments extending from the cell surface
    • Mediate bacterial attachment to host cells (important for infection)

    Bacterial Spores

    • Highly resistant structures formed under adverse conditions by Bacillus and Clostridium
    • Contain bacterial DNA, little water, and a thick, keratin-like coat

    Conclusion

    • Different species of bacteria have various structures and properties, making them important in medicine and ecology
    • Their structures are a crucial aspect of bacterial classification, identification and function.

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