Intensilight

Fluorescence imaging was carried out using Nikon Ti-E microscope with 100X CFI Apo TIRF objective with an NA of 1.49. All fluorescent probes were excited using a Nikon Intensilight, except for the photo-bleaching of lacI foci, which was excited by SpectraX LED single-spectrum light sources (Lumencor) with SpectraX filter sets (Lumencor). For imaging with Nikon Intensilight, the λ_ex/λ_bs/λ_em wavelengths of the filter cubes are as follows: SBFP2 and EBFP2 (363–391/425/435–485 nm), TagBFP (395–415/420/435–485 nm), mCerulean (426–446/455/460–500 nm), sfGFP (450–490/495/500–550 nm), mYpet and FlAsH (490–510/515/520–550 nm), TagRFP-T and mKO2 (530–560/562/570–620 nm), mCherry and mKate2 (540–580/585/592–668 nm), eqFP670 (589–625/649/655–1200 nm). For imaging with SpectraX, the excitation filters for orange and red proteins are respectively 555/25 nm (center/width, same below) and 575/22 nm. The multiband emission filters are respectively 435/26 – 510/40 – 595/40 – 705/72 nm, and 465/25 – 545/30 – 630/60 nm. The fluorescence signal was recorded by an Andor EMCCD camera (iXon Ultra 885), with an EM gain of 100. While our emission filter for the eqFP670 extends to the infrared region, eqFP670 does not fluoresce beyond 850 nm, which is well-within the detection range for most EMCCD cameras, including the one used in this study.

The microfluidic cell and worm images were captured at room temperature (∼25 °C) using an inverted microscope (Eclipse TE2000-U, Nikon, Japan) with × 4, × 10, × 20 and × 60 objectives (numerical aperture: 0.45). The images were captured by Nikon imaging software (NIS-Advanced, Nikon, Japan) using a Coolsnap CCD digital camera (CoolSNAP HQ2, Photometrics, USA). Movies were recorded by a Photron FASTCAM Viewer (PFV, Photron, USA) using a fast camera (Fastcam SA4, Photron, USA). For fluorescence imaging, a Nikon filter cube (excitation: 470 nm, emission: 515 nm) and a fibre optic illumination system (Intensilight, Nikon, Japan) were used.