**Core Concept:** Bacterial lysis refers to the destruction of bacterial cells in a culture, which can be caused by various factors such as antibiotics, host immune response, or bacteriophages (viruses). Bacteriophages are viruses that specifically infect bacteria and can cause their lysis.

**Why the Correct Answer is Right:** The correct answer, **D.** T4 bacteriophage, is a specific type of bacteriophage that infects and lyses Gram-negative bacteria, such as Escherichia coli. The process starts when the bacteriophage attaches to a receptor on the bacterial cell surface, followed by injection of the bacteriophage genetic material into the host cell. The bacteriophage then uses the host cell machinery to replicate its genetic material and synthesize bacteriophage proteins. These proteins assemble into new bacteriophage particles, which eventually burst out of the host cell, causing lysis.

**Why Each Wrong Option is Incorrect:**

A. **Bacteriophage T4 (Option D)** is the correct answer as it specifically lyses Gram-negative bacteria like Escherichia coli.

B. **Bacteriophage T7 (Option C)** is another bacteriophage that can infect and lyse some bacteria, but it primarily targets Gram-positive bacteria, not Gram-negative bacteria like Option D.

C. **Bacteriophage λ (Option B)** is a bacteriophage that primarily infects and lyses Gram-positive bacteria, not Gram-negative bacteria like Option D.

E. **Bacteriophage P22 (Option A)** is another bacteriophage that can infect and lyse some bacteria, but it primarily targets Gram-negative bacteria, not Gram-positive bacteria like Option C.

**Clinical Pearl:** Understanding bacteriophages and their roles in bacterial control is essential in microbiology and microbiological diagnostics. Bacteriophages can be used as biocontrol agents to combat antibiotic-resistant bacteria in various applications like food preservation, wastewater treatment, and even as a potential alternative to antibiotics in human medicine.