30 ml syringes

Bacterial cells were diluted to the OD₅₉₅ value of 1.0 before loading the cells into the device. To trap the cells in the growth channels, we mounted the device on the microscope stage. To load the cells into the inlet, we used 30 mL syringes (Terumo) driven by a syringe pump (As One) at a rate of 240 μL/h. The media syringe and the fluidic inlet were connected by a silicon tube with a 2 mm inner diameter. We used Teflon tubes to interface between the silicon tubes with 2 mm and 4 mm inner diameter inserted into the fluidic inlet. During the observation, the device was constantly supplied with a fresh medium from the inlet. All data were acquired using a DS-Fi3 camera sets attached to Nikon ECLIPSE Ts2R inverted microscope (Nikon, Tokyo, Japan). The microscope was equipped with an electric microscope stage (Prior Scientific KK, Cambridge, UK) to exchange the sample position during the observation. Nikon NIS-Elements AR software (ver. 5.20.02) controlled the camera, motorized stage, and fluorescent and brightfield shutters. To observe the S. aureus and S. enterica in the growth channels, we used 100× Oil Plan Apo (NA 1.45) and 60× Plan Apo (NA 0.95) objective lens (Nikon), respectively. GFP was monitored using a C-LEDFL470 LED light source (Nikon) and 470 nm C-LED filter (Nikon). Exposure times were adjusted to keep exposure light levels constant between experiments.