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?

Explanation

Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:1. Pseudomonas: Pseudomonas is a type of bacteria that possesses a cell wall and cannot be considered the smallest living cell without a definite cell wall. It is not pathogenic to animals and is aerobic, requiring oxygen for survival.2. Mycoplasma: Mycoplasma is a genus of bacteria that lacks a rigid cell wall and is known to be one of the smallest living cells. Some species of Mycoplasma are pathogenic to both plants and animals. They are also facultative anaerobes, meaning they can survive with or without oxygen.3. Nostoc: Nostoc is a genus of cyanobacteria (blue-green algae) that have a definite cell wall and do not fit the description of the smallest living cells without a cell wall. They are photosynthetic and can fix nitrogen.4. Bacillus: Bacillus is a genus of bacteria that possess a cell wall, and they are not the smallest living cells without a cell wall. They are aerobic bacteria and are not typically pathogenic to both plants and animals.So, Mycoplasma meets all the criteria mentioned in your question.