Strength and longevity of non-genetic memory in sister bacterial cells.

Phenotypic heterogeneity is a vital aspect of isogenic bacterial population related to the survival of the species. The focus of this study is to understand the origin of non-genetic phenotypic heterogeneity by observing the inheritance pattern of different cellular traits in the lineage of single bacterial cells using microfluidics and time-lapse microscopy. We aim to reveal the cellular factors responsible for this variability and estimate the timescale over which new phenotypes emerge. We have developed a unique microfluidic device that allows us to trap and follow E. coli sister cells for hundreds of generations in the same environment, and thus separating cellular effects from environmental ones. Our results reveal strong correlation of several measurable properties like cell size, cell-cycle duration and growth rate between E. coli sister cells for many generations while non-related cells growing in the same environment show almost zero correlation over the same period. These results allow us to quantitatively determine the strength and longevity of non-genetic memory in sister bacterial cells.