LC

Antibiotics and Bacteria

Gram (-) vs. Gram (+)

  • Gram-negative bacteria
    • Thin layer of peptidoglycan
    • Outer membrane is composed of endotoxins
    • Outer membrane contains porins that allow certain substances to pass
    • Periplasm is the space between the plasma and outer membrane
    • Gram-negative cells show up as pink in Gram stains
  • Gram-positive bacteria
    • Thick layer of peptidoglycan
    • No outer membrane
    • No porins
    • Gram-positive bacteria show up as purple in Gram stains

Bacteria Structures

  • Nucleoid: region in the cytoplasm that contains the bacteria’s DNA molecule
    • The bacterial chromosomal DNA is supercoiled
  • Plasmid: Circular and double-stranded DNA molecules
    • Plasmids can be transferred and typically contain genetic material for antibiotic resistance
  • Ribosomes: facilitate bonding of amino acids for protein synthesis
  • Cell Wall: Rigid wall that prevents lysis
    • Peptidoglycan contributes to the rigidity of the cell wall
  • Capsule (glycocalyx): allows attachment to surfaces and protection
  • Flagella: Protein appendages that move the bacteria
  • Pili: Filamentous appendages that allow for attachment
    • Involved in conjugation
  • Endotoxins: LPS molecules