This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Periplasmic space is seen in ? 
Select and explain. 
A. Gram positive bacteria, B. Gram negative bacteria, C. Acid fast bacteria, D. All
B: Gram negative bacteria
Answer: B: Gram negative bacteria 
Explanation: Ans. is 'b' i.e., Gram negative bacteria Periplasmic space is a narrow space between cytoplasmic membrane (plasma membrane) and cell wall. Periplasmic space has been more frequently and better recorded in gram-negative bacteria as compared to gram-negative. "At present most gram positive bacteria are thought to have only periplasm, but not periplasmic space".