Dm 100x 1.40 oil ph3

To visualise GFP-DnaN, starter cultures were grown overnight in defined minimal medium base (Spizizen minimal salts supplemented with Fe-NH₄-citrate (1 µg/ml), MgSO₄ (6 mM), CaCl₂ (100 µM), MnSO₄ (130 µM), ZnCl₂ (1 µM), thiamine (2 µM)) supplemented with casein hydrolysate (200 µg/ml) and glycerol (0.5%) with IPTG (1 mM) at 37°C, diluted 1:100 into fresh medium with IPTG (1 mM) and allowed to grow at 37°C for several generations until they reached an A₆₀₀ 0.3. Cells were collected by centrifugation, washed to remove IPTG, and resuspended into fresh medium at an A₆₀₀ 0.1 and allowed to grow until an A₆₀₀ 0.6. Cells were mounted on 1.5% agar pads (0.5X growth media) and a 0.13–0.17 mm glass coverslip (VWR) was placed on top. Microscopy was performed on an inverted epifluorescence microscope (Nikon Ti) fitted with a Plan-Apochromat objective (Nikon DM 100x/1.40 Oil Ph3). Light was transmitted from a 300 Watt xenon arc-lamp through a liquid light guide (Sutter Instruments) and images were collected using a CoolSnap HQ² cooled CCD camera (Photometrics). All filters were Modified Magnetron ET Sets from Chroma and details are available upon request. Digital images were acquired and analysed using METAMORPH software (version V.6.2r6). All experiments were independently performed at least twice and representative data is shown.