Which of the following microorganisms would be most damaged by exposure to hypotonic conditions?

• A. Staphylococcus aureus
• B. Bacillus subtilis
• C. Mycoplasma species
• D. Escherichia coli

Answer: (C)

Verified step by step guidance

1. Step 1: Understand what hypotonic conditions mean. In a hypotonic solution, the concentration of solutes outside the cell is lower than inside the cell, causing water to move into the cell by osmosis.
2. Step 2: Consider the structural differences of the microorganisms listed. For example, Staphylococcus aureus, Bacillus subtilis, and Escherichia coli all have rigid cell walls that help prevent excessive swelling in hypotonic environments.
3. Step 3: Recognize that Mycoplasma species lack a cell wall, which makes them more vulnerable to osmotic pressure changes because they cannot resist the influx of water.
4. Step 4: Analyze how the presence or absence of a cell wall affects the microorganism's ability to withstand hypotonic stress. Cells with walls maintain shape and prevent lysis, while those without are prone to bursting.
5. Step 5: Conclude that among the options, Mycoplasma species would be most damaged by hypotonic conditions due to their lack of a protective cell wall.