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

To investigate the non-gene tic variability of the division cycle and growt h of single cells, we compared pairs of Escherichia coli daughter cells' gr owth and division time under isolated conditions using a newly developed on -chip culture system. The advantages of the system are: (i) continuous cult ivation of isolated single cells or a group of cells in pm-sized micro-cage s under isolated contamination-free and exchangeable medium conditions, and (ii) continuous observation and comparison of those floating daughter cell s at a spatial resolution of 0.2 mum by phase-contrast/fluorescence microsc opy and digital image processing. Using this system, cell growth and divisi on time of daughter cells from an isolated mother cell were measured. A bro ad 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 distributio n of the division time and the division time differences suggests the invol vement of a probabilistic process to start the division.