Luria & Delbruck Thought Experiment #1 : Induction

Each of four cultures is started with a single bacterial cell. Each cell divides once per generation, producing two cells. At the end of 4 generations, 15 cell divisions produce 24 = 16 cells in each culture, for a total of 64 cells. 

In the final generation, each culture is exposed to the phage.  Most bacterial cells are sensitive (black). However, ten cells (3, 1, 5, & 1 in the four cultures) are observed to be resistant (blue). If resistance was induced by exposure to bacteriophage, and all cells have an identical chance of becoming resistant, then each culture is expected to have an equal number of resistant cells. If the average number of resistant cells per culture is small, the observed fluctuation among cultures will follow the Poisson Distribution, for which the variance equals the mean.

All text material ©2016 by Steven M. Carr