Bacterial Classification and Gram Staining
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Bacterial Classification and Gram Staining

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Questions and Answers

What is the primary concern of taxonomy?

  • Habitat preferences
  • Genetic similarities
  • Classification and nomenclature (correct)
  • Evolutionary relationships

    • Which of the following is NOT a level of classification in the taxonomic hierarchy?

  • Group (correct)
  • Species
  • Phylum
  • Class

    • In the binomial system of nomenclature, how is the genus name characterized?

  • Never capitalized
  • Always lowercase
  • Italics or underlined (correct)
  • Always abbreviated

    • What defines a species in sexually reproducing organisms?

    <p>Reproductive compatibility</p> Signup and view all the answers

    Which of the following correctly describes a 'strain' in microbial taxonomy?

    <p>A subgroup within a species with distinguishing characteristics</p> Signup and view all the answers

    What is the primary focus of Bergey’s Manual of Determinative Bacteriology?

    <p>Identification schemes based on morphological and biochemical tests</p> Signup and view all the answers

    Which resource primarily focuses on naming fungi?

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

    What characteristic defines bacterial cells compared to other organisms?

    <p>Single-celled structure without a nucleus</p> Signup and view all the answers

    Which database provides species names of known prokaryotes based on published articles?

    <p>Approved Lists of Bacterial Names</p> Signup and view all the answers

    What type of information does Bergey’s Manual of Systematic Bacteriology provide?

    <p>Phylogenetic information based on genetic sequencing</p> Signup and view all the answers

    What characteristic distinguishes prokaryotic cells like bacteria from eukaryotic cells?

    <p>Single, circular DNA molecule</p> Signup and view all the answers

    Which statement about fungi is most accurate?

    <p>Only a small percentage of fungi cause diseases in humans.</p> Signup and view all the answers

    Which type of organism does NOT belong to the class of parasites that can cause disease in humans?

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

    How do helminths differ from protozoa in terms of reproduction in humans?

    <p>Protozoa can multiply in humans, while helminths cannot.</p> Signup and view all the answers

    What type of infection is commonly caused by fungi in the lungs?

    <p>Tuberculosis-like infections</p> Signup and view all the answers

    Which of the following statements about ectoparasites is true?

    <p>They include organisms like ticks, fleas, and lice.</p> Signup and view all the answers

    Which of the following describes plasmids in bacteria?

    <p>Extra-chromosomal DNA that can confer advantageous traits.</p> Signup and view all the answers

    What is a primary challenge in treating protozoan infections?

    <p>They can reproduce rapidly while in the host.</p> Signup and view all the answers

    What characterizes a virus in its extracellular state?

    <p>It is known as a virion and is metabolically inert.</p> Signup and view all the answers

    Which statement about the origin of viruses is correct?

    <p>They may originate from pieces of nucleic acid or a past independent lifestyle.</p> Signup and view all the answers

    What are the primary factors used in virus classification?

    <p>Presence of lipid envelope and symmetry of the nucleocapsid.</p> Signup and view all the answers

    What defines a naked virus?

    <p>It is a virus that does not possess a surrounding lipid membrane.</p> Signup and view all the answers

    Which component of a virus is responsible for forming its protective shell?

    <p>Structural subunits of proteins assemble to form the capsid.</p> Signup and view all the answers

    When does a virus become enveloped?

    <p>When its nucleocapsid is enclosed in a lipid membrane.</p> Signup and view all the answers

    Which nucleic acid configuration can viruses possess?

    <p>Either DNA or RNA, but not both.</p> Signup and view all the answers

    What is the term for the complete complex of nucleic acid and protein in a virus?

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

    What is the primary function of lipopolysaccharides (LPS) in Gram-negative bacteria?

    <p>To maintain structural integrity and viability</p> Signup and view all the answers

    Which statement correctly describes the peptidoglycan structure in Gram-positive bacteria?

    <p>It has a thick layer ranging from 20-80 nm</p> Signup and view all the answers

    What role do teichoic acids play in Gram-positive bacteria?

    <p>They assist in nutrient uptake, specifically Mg2+</p> Signup and view all the answers

    The periplasmic space in Gram-negative bacteria is located between which two structures?

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

    How does the capsule contribute to the virulence of bacteria?

    <p>By providing protection from the host immune system</p> Signup and view all the answers

    Which of the following components is NOT typically found in Gram-positive bacteria?

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

    What distinguishes Gram-positive bacteria from Gram-negative bacteria in terms of cell wall structure?

    <p>Gram-positive bacteria have a thicker peptidoglycan layer outside the cell membrane</p> Signup and view all the answers

    Which function is NOT a role of the capsule found in bacteria?

    <p>Storage of nutrients</p> Signup and view all the answers

    Study Notes

    Bacterial Classification

    • Bacteria are single celled microbes
    • Lack a nucleus or membrane bound organelles
    • Cell wall is a mixed polymer of hexose sugars (N-acetylglucosamine and N-acetylmuramic acid) and amino acids
    • Bacteria are classified according to their cell wall as Gram-positive or Gram-negative.

    Gram pattern

    • In 1882, Christian Gram devised a bacterial staining method to visualize bacterial cell wall that allowed to differenciate bacteria in two major groups.
    • Gram positive bacteria have a thick peptidoglycan layer (20-80nm) external to the cell membrane
    • Gram negative bacteria have a thin peptidoglycan layer (5-10nm) overlaid by an outer membrane containing lipopolysaccharides and lipoprotein

    Lipopolysaccharide (LPS)

    • Conserved structure in all Gram-negative bacteria
    • Essential for structural integrity and viability of the bacteria
    • Also known as endotoxin because it induces a strong immune response in the host
    • Involved in other aspects of bacterial ecology, such as surface adhesion

    Other cell wall components

    • Teichoic acids: present in Gram positive bacteria, involved in uptake of Mg2+ by the cell
    • Teichuronic acids: similar polymers found in capsules or LPS in some Gram negative bacteria
    • Other: Lipids, proteins…

    Capsule

    • External to the cell wall
    • Composed of high molecular weight polysaccharides that give a slimy surface
    • Very important in virulence, as it protects the microorganism from the host immune system

    Nutrition

    • Process by which chemical substances (nutrients) are acquired from the environment and used in cellular activities.

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    Description

    This quiz delves into the fundamentals of bacterial classification, focusing on the key differences between Gram-positive and Gram-negative bacteria. It covers the structural characteristics of bacterial cell walls and the historical context of Gram staining as a method established by Christian Gram in 1882.

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