Scmos camera

Strains were cultivated overnight in the LB medium and sub cultured the next day until they reached the exponential growth phase (OD₆₀₀ = 0.2–0.3). Then, 5 μl of culture were spotted on an agarose pad [PBS buffer solified with 1% (w/v) agarose]. Fluorescence images were acquired using a Leica DMI 6000 B inverse microscope (Leica, Wetzlar, Germany) equipped with an SCMOS camera (Visitron Systems, Puchheim, Germany) and a HC PL APO 100×/1.4 oil PH3 objective. Image processing and analysis was carried out using the ImageJ-based Fiji tool (Schindelin et al., 2012 (link)).

Cells of CN-32 strains from overnight cultures were sub inoculated in 10 ml of LB with an OD₆₀₀ of 0.05. After reaching the exponential growth phase (OD₆₀₀ = 0.2–0.3), a 100 μl aliquot was placed under a coverslip fixed by four droplets of silicone (baysilone, VWR International GmbH, Darmstadt, Germany) to generate a space of 1–2 mm width. Movies of 120 frames were taken at room temperature with a Leica DMI 6000 B inverse microscope (Leica, Wetzlar, Germany) equipped with an SCMOS camera (Visitron Systems, Puchheim, Germany) and a HCX PL APO 100×/1.4 objective. The speed of at least 500 cells per strain was quantified using the MTrackJ plugin of Fiji (Meijering et al., 2012 (link)). Significance was tested using ANOVA (p = 0.05) in R version 3.0.1.