Help me with question 12 please 30 January 2017 Problem Set

30 January 2017 Problem Set 1 Biology 401 12. You are doing a viable cell count on a bacterial culture and you perform ten-fold serial dilutions as shown in Figure 4.14 of your text. You count 130 colonies that was on a plate spread with 0.05 ml of a 106 dilution of the original culture. How many viable ce per milliliter are there in the undiluted bacterial culture? 13. At the same time that you did the viable cell count of your bacterial culture (in problem 10). you also counted the cells in a Petroff-Hausser chamber, however, the cell count you obtained from Petroff-Hausser chamber is nearly double that obtained in the viable cel count. Based on this result, what might you conclude about the growth of the bacterial culture you are working with was it likely to be in lag phase, exponential or stationary phase. Explain your answer. 14. Doctors in a particular region of the country are inundated with patients who present with a flu-like disease that rapidly progresses in many cases to a fatal outcome. Epidemiologic analysis suggests that a transmissible agent causes the disease and it is found that all patients who succumb to the disease harbor a virus (named the vx virus) that is not found individuals who remain disease-free. Can we unambiguously conclude that the vx virus th causes the disease? not, describe how the observed results might be consistent with t vx virus not being the cause of the disease and what further evidence would be reguired prove that the vx virus truly caused disease.

Solution

Please find the answer below:

Dilution of the plate: 10^-6

Volume plated : 0.05 ml

Number of colonies appeared in the test plate: 130

Number of colony forming units in the plate (CFU/ml) = (Number of colonies appeared * volume plated) / dilution factor

CFU/ml = (130 * 0.05)/10^-6

or CFU/ml = 8.50 * 10⁶

Since we have divided the colony count with the dilution factor, the number of colonies appearing after the mathematical calculation represents the actual number of colonies in the undiluted sample.

Thus, the undiluted sample contains 8.5 * 10⁶ CFU/ml.