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Figure 4 | BMC Systems Biology

Figure 4

From: Noise and crosstalk in two quorum-sensing inputs of Vibrio fischeri

Figure 4

Microfluidic measurements of GFP fluorescence. (A) Schematic of microfluidic device for measuring lux expression in individual V.fischeri. Growth medium containing exogenous HSL flows through three parallel rectangular channels that are cast into the lower surface of a PDMS block. Live cells in channels adhere to the glass window (coverslip) that seals the channels from beneath, and are observed in an inverted microscope. The shallow ratio of channel height to width (h/w ~ 0.02-0.04) ensures a uniform flow velocity profile across the width and length of each channel. (B) Contour map of lux activation F versus HSL input. The white circles show HSL combinations applied to the cells during the microfluidic experiments described in the text. The contour labels show the activation fraction above the base level, i.e. (F-F0)/max(F-F0), as derived from the bulk measurements and competitive inhibition model. (C) Histogram comparing the correlation C ij (Eqn. (7)) in gfp expression of a pair of cells (i, j) to the physical separation r ij = √(x ij 2+y ij 2) between those cells. The color of each bin indicates the number of cell pairs (i, j) whose physical separation and brightness correlation fall within that bin. Pairs of near-neighbor cells are not more correlated in their lux activation than pairs of distant cells.

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