Space- and time-resolved protein dynamics in single bacterial cells observed on a chip.

Life cell imaging of bacterial cells over long times is very challenging because of the small dimensions and the need for a liquid environment assuring cell viability. In order to obtain space- and time-resolved information about protein dynamics, high resolution time-lapse fluorescence images (TLFI) of single bacterial cells were recorded in a poly(dimethylsiloxane) (PDMS) microfluidic chip. A new gradient coating technique was applied to ensure cell loading. As a proof-of-concept, we monitored the evenly distributed cytoplasmic protein GcrA as well as the asymmetric localization of the DivK protein in cells of S. meliloti over at least two division cycles. Localization of DivK was characterized by dividing each bacterial cell into 4 sections with dimensions closely above the optical limit of resolution. This approach of generating spatio-temporal resolved information of protein dynamics in single bacterial cells is applicable to many problems.