1. A laboratory technician mixes 1 mL of a stock culture with 99 mL of water. She then performs five 1/10 serial dilutions with 1 mL of the diluted stock culture. Before she goes home for the evening, she plates 0.1 mL of the final serial dilution and spreads the sample on a TSA plate containing 50 mL of solid agar. If she arrives to work the next day to find 295 colonies on the plate, what is the concentration of bacteria in the stock culture?
2. A stock sample of phage is diluted 1/10 one time and then diluted 1/1000 twice. A 0.1-mL portion of the final dilution is transferred to a test tube that contains 0.3 mL ofE. coli cells and 4 mL of molten agar. The tube's contents is mixed well and pouredonto a Petri dish of solid agar medium. After an overnight incubation, 158 plaques appear on the plate. What is the concentration of phage in the stock sample?