Why are mycoplasmas able to survive a relatively wide range of osmotic conditions, even though these bacteria lack cell walls?

Verified step by step guidance

1. Understand the typical role of the bacterial cell wall: It provides structural support and protection against osmotic pressure changes, preventing the cell from bursting in hypotonic environments.
2. Recognize that mycoplasmas lack a cell wall, which usually makes bacteria more vulnerable to osmotic stress because they cannot resist changes in external osmolarity through rigid structural support.
3. Identify the unique feature of mycoplasmas that compensates for the absence of a cell wall: their cell membrane contains sterols (such as cholesterol) that are incorporated from their environment.
4. Explain how sterols in the membrane increase membrane rigidity and stability, allowing mycoplasmas to maintain cell integrity and resist osmotic lysis despite lacking a cell wall.
5. Conclude that the presence of sterols in the plasma membrane is the key adaptation enabling mycoplasmas to survive a wide range of osmotic conditions.

Key Concepts

Mycoplasma Cell Structure

Mycoplasmas are unique bacteria that lack a rigid cell wall, possessing only a flexible plasma membrane. This absence of a cell wall makes them distinct from most bacteria and influences their shape and environmental interactions.

Osmotic Pressure and Cell Wall Function

In most bacteria, the cell wall provides structural support to resist osmotic pressure changes, preventing cell lysis in hypotonic environments. Without a cell wall, cells are generally more vulnerable to osmotic stress.

Adaptations of Mycoplasmas to Osmotic Stress

Mycoplasmas survive osmotic variations by having a sterol-rich plasma membrane that provides stability and flexibility. Additionally, they regulate internal solute concentrations to balance osmotic pressure, allowing survival without a cell wall.