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Microbiology: Bacterial Structure, Physiology, Growth, and Genetic Recombination

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Terms in this set (26)

  • Flagella in prokaryotes
    Locomotion/motility organelles that rotate from the basal body; composed of flagellin protein. Types include monotrichous, amphitrichous, lophotrichous, and peritrichous.
  • Axial filaments
    Found in spirochetes, anchored at one end and wrapped around the cell, producing a corkscrew motion for movement.
  • Pili (fimbriae)
    Hair-like structures on many Gram-negative bacteria used for adherence to surfaces and DNA transfer during conjugation.
  • Bacterial cell wall composition
    Made of peptidoglycan (N-acetyl glucosamine and N-acetyl muramic acid) with tetrapeptide side chains and peptide cross bridges.
  • Gram-positive cell wall
    Thick, multilayered peptidoglycan that stains blue/purple with Gram stain.
  • Gram-negative cell wall
    Thin peptidoglycan layer with an outer membrane containing lipids and sometimes Lipid A endotoxin; stains pink.
  • Bacterial cell membrane
    Phospholipid bilayer without sterols; functions in ATP synthesis, selective permeability, and photosynthesis in some bacteria.
  • Nucleoid
    Region containing circular, double-stranded DNA without a nuclear membrane or histones, attached to the cell membrane.
  • Plasmids
    Small circular DNA molecules independent of the chromosome; can carry genes like antibiotic resistance and replicate independently.
  • Bacterial ribosomes
    70S ribosomes composed of proteins and rRNA; target of some antibiotics; smaller than eukaryotic 80S ribosomes.
  • Endospores
    Dormant, resistant structures formed by some bacteria (e.g., Clostridium, Bacillus) to survive adverse conditions; formed by sporulation.
  • Capsule (glycocalyx)
    Mucopolysaccharide layer external to the cell wall that protects bacteria from host defenses like phagocytosis.
  • Bacterial shapes: Cocci
    Round-shaped bacteria; arrangements include diplococci, streptococci, and staphylococci.
  • Bacterial shapes: Bacilli
    Rod-shaped bacteria; arrangements include single bacilli, diplobacilli, and streptobacilli.
  • Bacterial shapes: Spiral
    Includes vibrio (curved rods), spirillum (rigid spirals), and spirochetes (flexible spirals).
  • Psychrophiles
    Cold-loving bacteria with optimum growth at about 15°C; found in polar regions and deep oceans.
  • Mesophiles
    Bacteria that grow best at moderate temperatures (25–40°C); most common cause of food spoilage and disease.
  • Thermophiles
    Heat-loving bacteria with optimum growth at 50–60°C; found in hot springs and sunlit areas.
  • Osmotic pressure effects on bacteria
    Hypotonic solutions cause swelling and bursting; hypertonic solutions cause plasmolysis and inhibit growth.
  • Bacterial oxygen requirements
    Categories include strict aerobes (require O2), strict anaerobes (no O2), facultative anaerobes (with or without O2), and microaerophiles (low O2).
  • Binary fission
    Primary method of bacterial reproduction; involves cell division with an average generation time of 1–3 hours.
  • Bacterial growth phases
    Lag phase (preparation), log phase (rapid growth), stationary phase (equilibrium), and death phase (decline).
  • Genetic recombination methods
    Includes transformation (uptake of DNA), conjugation (DNA transfer via pili), and transduction (DNA transfer via bacteriophages).
  • Transformation in bacteria
    Uptake of free DNA fragments or plasmids from the environment by a bacterial cell of the same species.
  • Conjugation
    Direct transfer of DNA between bacterial cells via pili; involves F+ (donor) and F- (recipient) cells.
  • Transduction
    Transfer of bacterial DNA from one cell to another by a virus (bacteriophage) acting as a vector.