Homework due Friday, 13 February 2015 Please refer to the table on the next page, and this equaAon (which Brendan introduced in class today!), N(t)=2t-­‐1 where N=populaAon size and t=Ame step, to address the following quesAons. 1.  Imagine that you are working with a bacterial culture, and find that there are 8 cells, total. If the populaAon was founded by 1 cell, how many Ames has the populaAon size doubled so far? 2. A culture is founded using a single Escherichia coli cell. If the populaAon is under opAmal condiAons, how many cells will there be 12 hours from now? 3. A sample contains 12,000 bacterial cells. How many Bacillus cereus cells will be present in 12 hours, assuming opAmal condiAons? Generation Time Under Optimal Conditions
(at 37oC)
Bacillus cereus
Escherichia coli
28 min
12.5 min
Staphylococcus aureus (causes many types of infections)
27-30 min
Mycobacterium tuberculosis (agent of Tuberculosis)
Treponema pallidum (agent of Syphilis)
Images: B. cereus, E. coli & S. aureus by T. Port;
TB culture, Dr. George Kubica PHIL #4428,
Treponema pallidum, Dr. Edwin P. Ewing, Jr., PHIL
18 – 24 hrs
30 hrs
From the Virtual Microbiology Classroom on