BIOL202 Week 6 Lab 6; Quantitation of Cultured Microorganisms

 Each question on the lab worksheet must be answered completely, thoroughly, in complete sentences and correctly in order to be considered for full credit  If the question asks you to do research or find a source, a reputable, credible and/or scholarly source citation must be included in order to be considered for full credit  If a math formula is required to arrive to an answer, work must be shown otherwise, no credit will be awarded Pre-Lab Questions 1. A serial dilution of a sample has an unknown concentration of microorganisms. A countable plate has 44 CFU. It was inoculated with 0.1 mL of a 10-1 dilution. What was the population density of the original sample per milliliter? (10 points) 2. Compare and contrast the plate count methods for bacterial and viral populations. (10 points) 3. Many of the quantitative methods discussed are popular because they enable the microbiology researcher to selectively count live cells only. Why do you think this might be an important or desirable feature in a medical or environmental research situation? Provide a scenario in which it might not be important to differentiate between live and dead cells when counting cell numbers. (10 points) Experiment 1 Results Tables  Table 1: Experiment 1 Growth Results (10 points) ***Enter only the number of colonies counted from each plate into the second row*** Experiment 1 Post-Lab Questions 1. What was the population density of the original sample? (use a countable plate to calculate this) (10 points) 2. Did all of the colonies on the countable plate(s) have a similar appearance? If not, how would you explain this? (5 points) 3. Describe a different quantitative method to estimate the number of microorganisms for this sample? What are the advantages and disadvantages for using this alternative method for this sample? (10 points) 4. What are some potential sources of error in the serial dilution/direct plate counting method? (10 points) 5. Per the USDA, whole, unpasteurized fresh eggs can contain no more than 50,000 CFU/mL bacteria in a standard plate count. You are curious if the fresh eggs that you buy from your neighbor are considered safe to consume so you use your eScience Microbiology kit to test these eggs using direct plate count after serial dilution. After you complete the experiment, you obtain 74 countable colonies from the 10-2 dilution plate. The inoculum volume you plated was 0.1 mL.(20 points) a. How many bacteria are present in 1 mL of the egg you sampled? b. Are these eggs considered safe to consume per USDA standards?