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Microbiology Unit 1 Key Concepts

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  • What are the three main types of microbes based on cellular structure?
    Prokaryotes (bacteria, archaea), Eukaryotes (fungi, protozoa, helminths), and Non-cellular (viruses, prions).
  • What distinguishes prokaryotes from eukaryotes?
    Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a nucleus and organelles.
  • How are microbes named in the binomial naming system?
    Microbes are named using Genus (capitalized) and species (lowercase), e.g., Escherichia coli.
  • What are the two primary methods used to classify microbes?
    Classification by phenotypic traits (morphology, staining) and genotypic methods (DNA sequencing).
  • What is a microbiome?
    A microbiome is the community of microbes living in a particular environment, such as the human body.
  • Define mutualism, commensalism, and parasitism in symbiotic interactions.
    Mutualism: both benefit; Commensalism: microbe benefits, host unaffected; Parasitism: microbe benefits, host harmed.
  • What is the difference between a true pathogen and an opportunistic pathogen?
    A true pathogen causes disease in healthy hosts; an opportunistic pathogen causes disease when host defenses are compromised.
  • What is dysbiosis and how can it cause disease?
    Dysbiosis is an imbalance in the microbiome that can lead to disease by disrupting normal microbial functions.
  • Define planktonic bacteria.
    Bacteria that are free-floating and not attached to a surface or each other.
  • What is a biofilm and why is it medically important?
    A biofilm is a community of bacteria attached to a surface, embedded in a protective matrix; biofilms are harder to eradicate and cause persistent infections.
  • Which bacterial form is more difficult to eradicate: planktonic or biofilm?
    Biofilms are more difficult to eradicate due to their protective matrix and resistance to antibiotics.
  • What are the two prokaryotic domains?
    Bacteria and Archaea.
  • Why are prokaryotic cells generally small?
    Small size allows efficient nutrient uptake and waste removal due to high surface area-to-volume ratio.
  • What is binary fission?
    Asexual reproduction where one bacterial cell divides into two identical daughter cells.
  • Do bacteria use spores for reproduction?
    No, bacterial spores (endospores) are for survival, not reproduction; binary fission is asexual reproduction.
  • What structural differences distinguish Gram-positive and Gram-negative bacteria?
    Gram-positive have thick peptidoglycan walls and teichoic acids; Gram-negative have thin peptidoglycan and an outer membrane with LPS.
  • Why are Mycoplasma species naturally resistant to penicillin?
    They lack a cell wall, so penicillin, which targets cell wall synthesis, is ineffective.
  • What is the function of the bacterial plasma membrane?
    Controls transport of materials in/out of the cell; contains proteins for nutrient uptake and energy production.
  • What are endospores and why do some bacteria produce them?
    Endospores are dormant, resistant structures formed to survive harsh conditions.
  • Name two medically relevant genera that can form endospores.
    Bacillus and Clostridium.
  • What is the endosymbiotic theory?
    Theory that eukaryotic organelles like mitochondria evolved from prokaryotes engulfed by ancestral cells.
  • Which eukaryotic organelle evolved from a photosynthetic prokaryote?
    Chloroplasts.
  • Which eukaryotic organelle evolved from a non-photosynthetic prokaryote?
    Mitochondria.
  • What are the four kingdoms of eukaryotic microbes?
    Animals (helminths), Fungi, Protists, and Plants (not on exam).
  • What are hyphae in fungi?
    Thread-like filaments that make up the body of multicellular fungi.
  • What is the difference between 70S and 80S ribosomes?
    70S ribosomes are in prokaryotes; 80S ribosomes are in eukaryotes.
  • Which microbes have a cell wall?
    Bacteria, archaea, fungi, and some protists have cell walls; animals do not.
  • What is the function of fimbriae?
    Fimbriae are used for attachment, not motility.