2. Students should identify the host that gave the most plaques as the most compatible (E. coli strain C). E. coli strain B should be second-most compatible.

3. Phi X 174 is known as a coliphage because it preferentially infects E. coli.

4. E. coli is strictly fecal. A positive plaque assay using E. coli strain C would indicate fecal contamination of the water. For more information visit www.epa.gov/microbes/1602ap01.pdf

5. See www.cellsalive.com/phage.htm and www.asmusa.org/pcsrc/mlp/movies/t4phage.mov for animation ideas. Suggest searching for figures depicting the lytic cycle of Phage T4 for script ideas. Suggest a range of 20-30 pages. If students have trouble, give them the following script:

6. Compatible viruses might be lurking inside the donor cell DNA. Since host species tend to be similar, these viruses are more likely able to infect the recipient species as well. While the virus may have evolved to be benign in the donor species, it may be prove more virulent in the recipient species.