Final answer:
The soft agar overlay is used in microbial phage research to grow bacteria and visualize phage infection. It is tempered to avoid shock that could disrupt the process. Agar solidifies the growth medium, allowing detailed analysis of bacterial and phage interactions.
Step-by-step explanation:
Soft Agar Overlay in Bacterial Phage Culturing
Soft agar overlay is used in microbiology to create a hospitable environment for bacteriophages (phages) to infect bacteria and to facilitate the formation of visible plaques. The tempering of soft agar is essential to protect the phage and bacteria from temperature shock, which could affect the infection process or kill the bacteria.
During experimentation, phages are allowed to infect bacterial cells. Post-infection, a blend containing the phage and bacterial suspension is centrifuged, separating the heavy bacterial cells and lighter phage particles.
In the Hershey-Chase experiment, phages labeled with radioactive substances were used to trace whether DNA or protein was the genetic material transmitted to bacteria. The results indicated that DNA, labeled with 32P, was found within the bacterial cell pellet, providing key evidence that DNA was the genetic material.