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Bacterial Cell Walls in Microbiology

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Termini in questo insieme (20)

  • Primary function of the bacterial cell wall

    Prevents osmotic lysis and contributes to pathogenicity.

  • Main component of bacterial cell walls

    Peptidoglycan, a polymer of repeating disaccharides N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).

  • Structure of peptidoglycan

    Rows of NAG and NAM linked by polypeptides forming a lattice structure.

  • How penicillin affects bacterial cell walls

    Interferes with the formation of peptide cross-bridges in peptidoglycan.

  • Gram stain mechanism in Gram-positive bacteria

    Alcohol dehydrates thick peptidoglycan, trapping crystal violet-iodine (CV-I) crystals, staining cells purple.

  • Gram stain mechanism in Gram-negative bacteria

    Alcohol dissolves outer membrane and washes out CV-I crystals; cells are counterstained pink with safranin.

  • Characteristics of Gram-positive cell walls

    Thick peptidoglycan layers with teichoic acids linking to plasma membrane and peptidoglycan; negatively charged.

  • Role of teichoic acids in Gram-positive bacteria

    Link cell wall to plasma membrane and peptidoglycan; contribute to negative charge.

  • Susceptibility of Gram-positive bacteria to antibiotics and enzymes

    Highly susceptible to penicillin and lysozyme.

  • Characteristics of Gram-negative cell walls

    Thin peptidoglycan in periplasmic space and an outer membrane made of LPS, lipoproteins, and phospholipids.

  • Components and functions of Gram-negative outer membrane

    Contains LPS (O polysaccharide antigen and Lipid A endotoxin), protects from phagocytes, complement, and antibiotics.

  • Function of porins in Gram-negative bacteria

    Porins are proteins that form channels allowing molecules to pass through the outer membrane.

  • Toxin production in Gram-negative bacteria

    Produce both endotoxins (Lipid A) and exotoxins.

  • Susceptibility of Gram-negative bacteria to penicillin and lysozyme

    Low susceptibility due to protective outer membrane.

  • Features of acid-fast bacterial cell walls

    Thick peptidoglycan with mycolic acid (waxy lipid) bound; stain with carbolfuchsin which resists acid-alcohol decolorization.

  • Examples of acid-fast genera

    Mycobacterium and Nocardia.

  • Characteristics of mycoplasmas

    Lack cell walls; have sterols in plasma membrane that protect from lysis.

  • Cell wall characteristics of archaea

    Either wall-less or have walls made of pseudomurein, which lacks NAM and D-amino acids.

  • Effect of lysozyme on bacterial cell walls

    Digests portions of peptidoglycan, weakening the cell wall.

  • How penicillin damages bacterial cell walls

    Inhibits formation of peptide bridges in peptidoglycan, preventing proper cell wall synthesis.