Estimation of mutation rates in antibiotic research

Luria and Delbruck identified that the frequency of mutation was subject to considerable fluctuation. They argued that the large fluctuation in the number of organism surviving exposure to bacteriophage meant that resistance was acquired through mutation rather than a physiological adaptation to the bacteriophage. Mutations that arose early in the broth culture would give rise to a "Jackpot culture" (1). Thus the size of a lineage of mutant cells depends on when the mutation occurred. It is said that the original idea came to Luria while he was observing a slot machine in Bloomington, IN (2). Early mutations are rare (like jackpots with a slot machine) thus when a series of cultures are compared the numbers of mutants would have "a distribution with an abnormally high variance" (1).