Fig. 4
From: Chemotaxis of Escherichia coli to major hormones and polyamines present in human gut
Chemotactic response in gradients of gut compounds. Chemotactic drift (defined as vch/αv0, see Methods) was measured in gradients of dopamine (Dop), NE, DHMA (DH), epinephrine (Epi), melatonin (Mel) or spermidine (S) established in a microfluidic device (Inset; measurement area is indicated by an orange rectangle). Zero chemotactic drift corresponds to non-responding cells and one to direct swimming up (negative values) or down (positive values) the gradient. For the negative control (∅), drift of the wild-type cells was measured in buffer in the absence of gradients. For the positive control, the drift was measured in a gradient of 0–1 mM aspartate (Asp). As a reference (not shown), the chemotactic drift of the wild-type cells in a gradient of non-metabolized attractant MeAsp had an average value of −0.1 [52]. Error bars indicate the standard error of the mean. A one-tailed student t-test was performed to assess the significance of the response being different from 0 (**P ≤ 0.05; *P ≤ 0.1)
