Statistical Study of Cellular Aging

Abstract

Whereas aging is obvious in macroscopic organisms, it is not in single-celled ones, such as the model organism E. Coli, where one has the best chances of describing and quantifying the molecular process involved. To determine if E. Coli experiences aging related to the inheritance of the old pole, E. J. Stewart et al. [1] followed 94 individual exponentially growing cells through up to nine generations, determining the complete lineage and the growth rate of each cell. Averaging over these 94 experiments leads the authors to the conclusion that the two supposedly identical cells produced during cell division are functionally asymmetric. This preliminary study, avoiding inter-experiment averaging, aims at reasoning experiment-wise and describing the structure of dependency within a lineage of E. Coli. We propose a single-experiment model for the dynamics of such a lineage of growth rates. We fit it to the data and perform experiment- wise tests which lead us to accept that the old pole progeny cell experiences slowed growth rate and hence should be considered an aging parent repeatedly producing rejuvenated offspring. Eventually, as a first step towards answering statistical questions about markovian models on binary trees, we run simulations of the model and conjecture results. At this preliminary stage, we have not used the results on bifurcative autoregressive models [2] which seem to be an appropriate background for the gaussian model. R´