Phage Typing Learning Objectives 1. Explain the purpose of phage typing. 2. Describe the phage typing method. 3. Explain what is occurring when plaques form in a bacterial lawn. 4. If both T4 and ΦX174 use LPS as their bacterial receptor, explain why wild-type phage T4 produces plaques, while wild-type ΦX174 does not infect E. coli K-12. Identification of Unknowns 1. Why is a streak plate important for a bacterial unknown analysis? What is an additional early analysis step? 2. Describe the Enterobacteriaceae and their major characteristics. 3. Describe the test series/battery typically used to distinguish between members of the Enterobacteriaceae. 4. Explain what the symbols (+) and (-) indicate regarding the outcome of various biochemical tests. 1. Identify the 3 groups of soil organisms isolated in the soil microbial count. Explain how these groups were separated for analysis. 2. Identify the major antibiotic-producing genera found in the soil, and, for each, identify the above group to which it belongs. 3. Explain why dilutions are necessary for microbial counts. 4. Starting with a culture containing 106 cells/ml, describe in detail how to set up a serial dilution scheme to result in a countable plate. 5. Evaluate and interpret the results of a plate count, including selecting the appropriate plate for counting, and calculating the original cell density (OCD). 6. Identify three bacterial pathogens transmitted through fecal contamination of water. 7. Explain the difference between coliform and non-coliform bacteria. Identify the coliform organisms used as indicator species for fecal contamination of water. 8. Describe in detail the technique commonly used to assess the presence of fecal coliforms in water. Specify what constitutes a countable plate. 9. Identify the selective medium used to enumerate fecal coliforms and the basis for its selectivity. Describe the appearance of coliforms on this medium. 10. Given a countable plate, calculate the coliform CFU per 100 mL. Specify the coliform count of potable water.