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Microbiology: Classification and Identification of Microorganisms

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  • What is taxonomy in microbiology?
    Taxonomy is the science of classifying organisms to reflect their similarities and evolutionary relationships.
  • Define phylogeny.
    Phylogeny is the evolutionary history and relationships among organisms.
  • What are the three domains of life according to Woese's system?
    Bacteria, Archaea, and Eukarya based on rRNA sequences and molecular evidence.
  • Key difference in cell wall composition between Archaea and Bacteria?
    Archaea have cell walls that vary in composition and lack peptidoglycan, while Bacteria have cell walls containing peptidoglycan.
  • What is the first amino acid in protein synthesis for Archaea and Bacteria?
    Archaea use methionine, while Bacteria use formylmethionine.
  • Describe the endosymbiont theory.
    Eukaryotic organelles like mitochondria and chloroplasts originated from prokaryotic cells living inside ancestral eukaryotes.
  • How do prokaryotic and eukaryotic cells differ in DNA structure?
    Prokaryotes have one circular DNA molecule, while eukaryotes have linear DNA.
  • What is the taxonomic hierarchy from broadest to most specific?
    Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
  • What is binomial nomenclature?
    A system assigning each organism a two-part name: Genus (capitalized) and species (lowercase), both italicized.
  • What is Bergey’s Manual used for?
    It is the standard reference for prokaryotic classification and identification based on morphology, staining, and biochemical tests.
  • How does Gram staining differentiate bacteria?
    It differentiates bacteria based on cell wall properties, classifying them as Gram-positive or Gram-negative.
  • What is the principle of the slide agglutination test?
    Bacteria clump when mixed with specific antibodies, indicating a positive antigen-antibody reaction.
  • What does ELISA detect in microbiology?
    ELISA detects antigens or antibodies in a sample for rapid diagnostics.
  • What is phage typing used for?
    Determines bacterial susceptibility to specific bacteriophages for epidemiological tracing.
  • How does flow cytometry help in microbial identification?
    Analyzes physical and chemical characteristics of cells using lasers to distinguish species often without culturing.
  • What does nucleic acid hybridization measure?
    The ability of DNA from different organisms to hybridize; >70% hybridization indicates the same species.
  • What is the role of PCR in microbial identification?
    PCR amplifies DNA for identification, even from unculturable organisms.
  • What is a dichotomous key?
    A tool for identification based on a series of choices between two alternatives.
  • What is a cladogram?
    A branching diagram depicting evolutionary relationships based on genetic data.
  • How do Archaea membrane lipids differ from Bacteria?
    Archaea have branched carbon chains attached by ether linkages, while Bacteria have straight chains with ester linkages.