This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Microbiology
An aliquot of Escherichia coli is treated with ethylenediaminetetraacetic acid (EDTA). The first wash is analyzed and found to contain alkaline phosphatase, DNase, and penicillinase. The anatomic area of the cell affected by the EDTA is most likely to have been the 
Select and explain. 
A. Periplasmic space, B. Mesosomal space, C. Chromosome, D. Plasma membrane
A: Periplasmic space
Answer: A: Periplasmic space 
Explanation: The periplasm is the space between the outer membrane and plasma membrane of bacteria. The periplasmic space in Escherichia coli has been shown to contain a number of proteins, sugars, amino acids, and inorganic ions. Ethylenediamine-tetra acetic acid (EDTA) is a chelating agent that disrupts the cell walls of Gram-negative bacteria.