Oneview

AuNPs (15.5 nm)
were synthesized
as described previously.^{26 (link)} The size and
distribution of AuNPs were determined by dynamic light scattering
(DLS) with a Zetasizer instrument (Malvern Instruments). The samples
were diluted to a concentration of 5 nM in Milli-Q water and transferred
to disposable plastic cuvettes at room temperature. The samples were
measured in triplicate, and the hydrodynamic radius was calculated
using Stoke–Einstein’s relation for the Brownian motion
of particles. Particle size and morphology were further analyzed using
transmission electron microscopy (TEM). The samples were lyophilized
for 24 h on TEM grids of 150 mesh (Agar Scientific AGG201N) and images
acquired using a Fei Tecnai 12 TE microscope and imaged with a 16
megapixel Gatan OneView camera with CMOS sensors. Images were obtained
using a 1 s exposure time and a pixel saturation of 5000–6000.
Analysis was performed using ImageJ software.

Cells were observed on a 24 × 50 mm coverslip under a 0.15% agarose-PYE “pad” to immobilize the cells. Samples were observed, thanks to an epifluorescent-inverted microscope Nikon Eclipse TiE E PFS (100 × oil objective NA 1.45 Phase Contrast). Cells morphologies and fluorescent images were analyzed using ImageJ and MicrobeJ [37 (link),73 (link)]. Stalk length was measured by using BacStalk software [75 (link)]. Electron microscopy (EM) was performed by placing 5 μL drops of the bacteria suspension for 3 min directly on glow discharged carbon coated grids (EMS). The grids were then washed with 2 drops of 2% aqueous uranyl acetate and stained with a third drop for 2 min. Grids were dried on filter paper and the samples were analyzed using a Tecnai 200KV electron microscope (FEI), and digital acquisitions were made with a numeric camera (Oneview, Gatan).