Question

An apple pie has 2 million (2 x 10^6) Staph. aureus cells in it. The food preparer did not wash his hands and probably inoculated the cream with 200 Staph. aureus. He also forgot to refrigerate it. If the pie was made 6 hours ago, how many generations have occurred? How long is each generation? Using the generation 2number of generations x initial number of bacteria = total # of bacteria present after n generations time you calculated, how many bacteria would be present after 8 hours at room temperature

Answer 1

Step-by-step explanation:

given cells at incubation = 2 million (2 x 10^6) Staph

cells at the start of incubation = 200 Staph

Total time =6hrs = 360minutes

Recalling that Number of generations = Log(cells at incubation) - Log (cells at the start of incubation)/0.301

• Number of generations = Log 2000000 - log 200 /0.301

= 20.93 generations.

• hence generation time = total time/number of generations

= 360/20.93 = 17.20minutes

as said, that the apple pie is left after 2hrs, it implies 8hrs (480minutes) will be the new total time; number of generations = total time / generation time

= 480/17.20minutes = 27.90 generations

• hence total number of bacteria after 8hrs = 2^n generations x initial number of bacteria

= 2^27.90 x 200 staph = 5.009 x 10^10 bacteria