Non-genetic variability of division cycle and growth of isolated individual cells in on-chip culture system

To investigate the non-genetic variability of the division cycle and growth of single cells, we compared pairs of Eschertchia coli daughter cells' growth and division time under isolated conditions using a newly developed on-chip culture system. The advantages of the system are: (i) continuous cultivation of isolated single cells or a group of cells in μm-sized micro-cages under isolated contamination-free and exchangeable medium conditions, and (ii) continuous observation and comparison of those floating daughter cells at a spatial resolution of 0.2μm by phase-contrast/fluorescence microscopy and digital image processing. Using this system, cell growth and division time of daughter cells from an isolated mother cell were measured. A broad distribution of the cell division time and the division time differences of two daughter cells from the same mother cells were found. They are not attributable to a difference in DNA. The same tendency of broad distribution of the division time and the division time differences suggests the involvement of a probabilistic process to start the division.