Atypical Bacterial Cell Walls

Overview

• Discusses atypical cell walls in bacteria.
• Contrasts with gram-positive and gram-negative cell walls which are covered in another video.

Wall-less Bacteria

• Key Genus: Mycoplasma.
  • Do not need cell walls.
  • Known as the smallest bacteria able to reproduce outside a host cell.
  • Characteristics that allow them to lack cell walls:
    1. Size: Extremely small, almost virus-like.
    2. Sterols in Plasma Membrane:
       • Similar to cholesterol found in human cell membranes.
       • Provides structural support without the need for a cell wall.

Acid-Fast Bacteria

• Sometimes labeled as "gram-positive" but do not stain with Gram stain due to unique cell wall composition.
• Cell Wall Composition:
  • Contains a waxy layer of mycolic acid.
  • Makes up to 60% of the cell membrane.
  • Hydrophobic and water-repelling, preventing Gram staining.
• Key Genera and Species:
  • Mycobacterium:
    • Notable Species: Mycobacterium tuberculosis (causes TB), Mycobacterium leprae (causes leprosy/Hansen’s disease).
  • Nocardia:
    • Pathogenic strains are rare.

Summary

• Atypical cell walls include wall-less bacteria like mycoplasmas and acid-fast bacteria with mycolic acid layers.
• Highlighted the significant differences and reasons behind the absence or alteration of cell walls in these bacteria.

Conclusion

• Clarifies the distinctions in cell wall structures among different bacterial types.
• Serves as an additional resource to understand atypical bacterial cell walls beyond standard gram classification.