Question

Which among the following are the smallest living cells, known without a definite cell wall, pathogenic to plants as well as animals and can survive without oxygen?

• A. Bacillus
• B. Pseudomonas
• C. Mycoplasma
• D. Nostoc

Answer 1

The Correct Option is C

The question asks about the smallest living cells known to lack a definite cell wall, are pathogenic to both plants and animals, and can survive without oxygen. Let's analyze the options given:

1. Bacillus: This is a genus of bacteria known for their rod-like shape. They typically have a rigid cell wall and are aerobic or facultatively anaerobic, meaning they generally require oxygen.
2. Pseudomonas: A genus of bacteria that are gram-negative and possess a flexible cell wall. They are known to be aerobic, requiring oxygen for growth.
3. Mycoplasma: These are the smallest known living cells that lack a definite cell wall, making them unique among bacteria. They are also known for being pathogenic to both plants and animals. Mycoplasma can survive without oxygen because they are facultative anaerobes.
4. Nostoc: A genus of cyanobacteria that are photosynthetic and generally possess a cell wall. They are not known for their pathogenicity and require light for photosynthesis, indicating a need for oxygen as they are primarily aerobic.

By analyzing these options, it's clear that the Mycoplasma fits all the characteristics mentioned in the question: smallest living cells, lacking a definite cell wall, pathogenic, and able to survive without oxygen. The other options either do not fit the given characteristics completely or possess features that exclude them from being the correct answer.

Thus, the correct answer is Mycoplasma.