Kinship Effects in Stochastic Antibiotic Killing of Bacteria.

Antibiotic susceptibility is a complex trait that varies from cell to cell, even when the cells are genetically identical. Our previous research indicated that antibiotic killing is in large part stochastic. Here, we directly quantified the degree of stochastic killing. We grew Escherichia coli cells in media containing a b-lactam drug, cefsulodin. We analyzed the growth and death of individual cells and turned the dataset into a genealogical tree, precisely identifying the relationship between bacterial cells. We then calculated pairwise correlation in the survival rates of related cells, starting with siblings, and moving on to more distant relatives such as aunt/niece, first cousins, and so forth. We found a statistically significant correlation for the survival of siblings, but none for more distant relationships. We also found that cells which inherit a pole that is several generations old have a survival advantage over cells with new poles.