UC San Diego

Escherichia coli elongates as a rod-shaped bacterium and initiates binary fission by pinching in the mid-cell region. The end result of a single “mother cell” undergoing division is the birth of two daughter pairs – an old and a new daughter. The two daughters then repeat this life cycle by elongating and splitting into two more daughters. The process of aging and rejuvenation in bacteria leads to mothers producing offspring with unequal fitness, measured

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in growth rate and mortality under stress, favoring the new daughter. Besides affecting the reproductive rate and survival, it was hypothesized that bacterial aging could also strongly influence or even determine the length at which E. coli cells in a population are born.

By implementing microfluidic techniques into single-cell time lapse microscopy experiments, it was found that E. coli newborn daughters resulting from an aged mother are asymmetric with respect to cell length at birth, with the old daughter born significantly longer than the new daughter. New mothers produced two newborn daughters that were not significantly different from each other in length, and on average were shorter than the old offspring from an old mother. We show that history of old and new pole inheritance also has an effect on cell size at a single-cell level. Single-cell data showed that there was a deviation away from a previously posited adder model of size homeostasis, and this deviation is amplified when looking at aged and rejuvenated cells.