Fluoroshield dapi medium

Dissection, fixation and immunostaining were performed as described by [68 (link)]. The following antibodies were used: mouse anti-Prospero (MR1A-c, Developmental Studies Hybridoma Bank (DSHB)) at 1:200; mouse anti-Arm (N2 7A1-s, DSHB) at 1:50; rabbit anti-Caspase3 (Cell Signaling, #9661) at 1:300; rabbit anti-DH31 (gift from Jan Veenstra [40 (link)]) and Michael Nitabach [31 (link)]) at 1:500. The secondary antibodies used were anti-mouse Alexa647, anti-rabbit Alexa488, anti-rabbit Alexa546 (Invitrogen). All secondary antibodies were used at 1:1000. Phalloidin-Alexa555 (Molecular Probes, A34055) were used at 1:500 2h at room temperature or 1:2000 overnight at 4°C. Guts were mounted in Fluoroshield-DAPI medium (Sigma) and observed with a Zeiss Axioplan Z1 with Apotome 2 microscope. Pictures in Fig 4M and 4N were acquired using a Zeiss LSM 880 confocal equipped with a Fast AiryScan. Images were analyzed using ZEN (Zeiss) and Photoshop software. Image acquisition was performed at the Microscopy platform of the Institut Sophia Agrobiotech (INRA 1355-UNS-CNRS 7254-Sophia Antipolis).

Dissection, fixation and immunostaining were performed as described by Micchelli, 2014 (link). Dilutions of the various antibodies were: mouse anti-Armadillo N27A1 at 1:50 (DSHB), mouse anti-Connectin-C1-427 at 1/200 (DSHB), mouse anti-Prospero MR1A at 1:200 (DSHB), rabbit anti-PH3 at 1:1000 (Millipore, 06–570), Rabbit anti-Cleaved Caspase-3 at 1/600 (Cell Signalling Asp175 #9661), Goat anti-mouse AlexaFluor-647 at 1/500 (Molecular Probes Cat# A-21235), Goat anti-mouse AlexaFluor-546 at 1/500 (Molecular Probes Cat# A-11003), Goat anti-rabbit AlexaFluor-647 at 1/500 (Thermo Fisher Scientific Cat# A32733), Goat anti-rabbit AlexaFluor-546 at 1/500 (Thermo Fisher Scientific Cat# A-11010). For microscopy, guts were mounted in Fluoroshield DAPI medium (Sigma, # F6057) and immediately observed on a Zeiss Axioplan Z1 with Apotome 2 microscope. Images were analyzed using ZEN (Zeiss), ImageJ and Photoshop software. Image acquisition was performed at the microscopy platform of the Sophia Agrobiotech Institute (INRAE1355-UCA-CNRS7254 – Sophia Antipolis).

Membrane integrity and nuclear morphology of Caco-2 cells were analysed by fluorescent phalloidin (F-actin) and Dapi (DNA) stainings. Cells were grown on sterile glass cover slips in 6-well plates then treated with EcN strains and controls (MG1655 and 0.1 mM camptothecin; Sigma) as described above (analysis of apoptosis). After the treatments, the cells on coverslips were washed with PBS then fixed with 4% formaldehyde (Sigma) in PBS for 20 min at RT. The fixed cells were washed three times with PBS and permeabilised with 0.1% Triton X-100 (Sigma) in PBS for 5 min at RT. The cells were washed three times with PBS, 5 min per wash with gentle rocking, then treated with a 0.1 μg ml^–1 solution of fluorescein isothiocyanate-phalloidin (Sigma- Aldrich) in PBS for 1 h at RT in the dark. The cells were washed twice with PBS and were mounted with the Fluoroshield DAPI medium (Sigma) and examined under a Leica TCS SP5 Confocal Laser Scanning microscope (Leica Microsystems, Wetzlar, Germany).