Dm1000 model microscope

Exponential cultures of the L. plantarum strains were sedimented by centrifugation and resuspended in saline solution (0.85% w/v NaCl) to obtain a 10-fold concentrated suspension. Subsequently, a 5 μL aliquot of the suspensions was directly analyzed without fixation by phase contrast or fluorescence microscopy. A Leica DM1000 model microscope (Leica Microsystems, Mannheim, Germany) with a light source EL6000 and the filter system TX2 ET was used for detection of the mCherry fluorescence. The microscope was connected to a DFC3000G camera (Leica Microsystems) with a CCD sensor. Image analysis was performed with the Leica Application Suite X software (Leica Microsystems).

Exponential cultures of P. parvulus strains and V. anguillarum NB10[pOT11] were sedimented and concentrated fivefold by resuspension in PBS pH 7.2. Then, without fixing, the suspension (10 μL) was used for phase contrast and fluorescent microscopy analysis with a Leica DM1000 model microscope (Leica Microsystems, Mannheim, Germany) with a light source EL6000 and the filter system TX2 ET and GFP ET for detection of mCherry and GFP fluorescences, respectively. The microscope was connected to a DFC3000G camera (Leica Microsystems) with a CCD sensor. The image analysis was performed using Leica Application Suite X Software (Leica Microsystems).
Cultures of 2.6[pRCR12] and 2.6NR[pRCR12], prepared as described for binding to Caco-2 cells assay (see below), were used for electron microscopy analysis. A drop from each bacterial solution resuspended in 0.1 M AcNH₄, pH 7, was deposited on a carbon film copper grid, which had previously been hydrophilized by a glow discharge process for 1 min, and rinsed in water during 15 s. Then, the grid was stained during 10 s with a uranyl acetate water solution (0.2% w/v) in order to improve the image contrast, and finally, rinsed again in water. The sample was air-dried and examined in a JEOL JEM-1230 microscope (JEOL, Peabody, MA, United States), operating at an accelerating voltage of 100 kV.

Exponential cultures of the L. plantarum strains were sedimented and resuspended in PBS pH 7.2 to obtain a fivefold concentrated suspension. Then, without fixing, the suspensions (10 μL) were used for phase contrast and fluorescent microscopy analysis with a Leica DM1000 model microscope (Leica Microsystems, Mannheim, Germany) with a light source EL6000 and the filter system TX2 ET for detection of mCherry fluorescence, respectively. The microscope was connected to a DFC3000G camera (Leica Microsystems) with a CCD sensor. The image analysis was performed using Leica Application Suite X Software (Leica Microsystems).