Understanding Differences Between Bacteria and Mycoplasma

Bacteria and Mycoplasma are both types of microorganisms, specifically prokaryotes, but they have some significant differences in their structure and composition.

Let's look at the options provided and see how bacteria and mycoplasma compare:

• Nucleoides: Both bacteria and mycoplasma contain their genetic material (DNA) in a region within the cytoplasm called the nucleoid. They do not have a membrane-bound nucleus. So, having a nucleoid is common to both and is not a difference.
• Plasma membrane: Both bacteria and mycoplasma have a plasma membrane that encloses the cytoplasm and controls the movement of substances in and out of the cell. This is a fundamental structure present in both.
• 70-S ribosome: Prokaryotic cells, including both bacteria and mycoplasma, have 70S ribosomes. These are the structures responsible for protein synthesis. Eukaryotic cells, in contrast, have 80S ribosomes. So, the presence of 70S ribosomes is a similarity, not a difference.
• Rigid cell wall: This is the key difference. Most bacteria have a rigid cell wall, typically composed of peptidoglycan, which provides structural support, protects the cell from osmotic lysis, and maintains its shape. Mycoplasma, on the other hand, completely lack a cell wall. This absence of a rigid cell wall makes mycoplasma pleomorphic (able to change shape) and also makes them resistant to antibiotics that target cell wall synthesis (like penicillin).

Therefore, the presence of a rigid cell wall is a characteristic feature of most bacteria that is absent in mycoplasma.