  We have developed a method combining microfluidics, time-lapsed
single-molecule microscopy and automated image analysis allowing for the
observation of an excess of 3000 complete cell cycles of exponentially growing
Escherichia coli cells per experiment. The method makes it possible to analyze
the rate of gene expression at the level of single proteins over the bacterial
cell cycle. We also demonstrate that it is possible to count the number of
non-specifically DNA binding LacI-Venus molecules using short excitation light
pulses. The transcription factors are localized on the nucleoids in the cell
and appear to be uniformly distributed on chromosomal DNA. An increase of the
expression of LacI is observed at the beginning of the cell cycle, possibly
because some gene copies are de-repressed as a result of partitioning
inequalities at cell division. Finally, observe a size-growth rate uncertainty
relation where cells living in rich media vary more in the length at birth than
in generation time and the opposite is true for cells living in poorer media.
