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

**Core Concept**
EDTA is a chelating agent that binds to divalent cations, disrupting various cellular processes that rely on these ions. In the context of bacterial cells, EDTA is often used to assess the integrity of the outer membrane, which is rich in divalent cations.

**Why the Correct Answer is Right**
The presence of alkaline phosphatase, DNase, and penicillinase in the first wash suggests that the outer membrane of the Escherichia coli cell has been compromised. Alkaline phosphatase is a periplasmic enzyme, while DNase and penicillinase are both associated with the outer membrane. EDTA's chelation of divalent cations disrupts the lipopolysaccharide layer of the outer membrane, leading to the release of these enzymes. This is because the lipopolysaccharide layer relies on divalent cations (such as Mg²⁺ and Ca²⁺) to maintain its structure and function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
The use of EDTA to assess the integrity of the outer membrane is a crucial technique in understanding bacterial physiology and the mechanisms of antibiotic action. This method can help differentiate between outer membrane-permeabilizing antibiotics and those that target other cellular processes.

**Correct Answer:** C. Periplasmic space.

✓ Correct Answer: A. Periplasmic space