Lost and found
Today is Alexander Fleming's 133th Birthday one of the greatest biologists in the history, known throughout the world for discovering penicillin, above, its schematic mechanism, and below its explanation:
- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium with a dividing bacterium.
- The cell begins to grow, but is unable to synthesize new cell wall to accommodate the expanding cell.
- As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall.
- Cell wall integrity is further violated. The cell continues to increase in size, but is unable to “pinch off” the extra cytoplasmic material into two daughter cells because the formation of a division furrow depends on the ability to synthesize new cell wall.
- The cell wall is shed entirely, forming a spheroplast, which is extremely vulnerable relative to the original cell. The loss of the cell wall also causes the cell to lose control over its shape, so even if the original bacterium were rod-shaped, the sphereoplast is generally spherical. Finally, the fact that the cell has now doubled much of its genetic and metabolic material further disrupts homeostasis, which usually leads to the cell’s death.