Transmission electron microscopy of phage ICBM5

To prepare for transmission electron microscopy (TEM), 30 µl of CsCl-purified ICBM5 stock were pipetted on top of a carbon-coated grid (Formvar 162, 200 mesh) and phages were allowed to absorb for 3 min. This was followed by staining with 30 µl 2 per cent uranyl acetate for 45 s and gentle removal of the liquid with filter paper. After air-drying for 15 min, the grids were visualized with the transmission electron microscope Zeiss EM902A. Images were documented with the Proscan High-Speed Slow Scan Charge Coupled Device (SSCCD) camera and analyzed using the software ImageSP viewer (Version 1.2.5.16). Negatively stained phages were used for capsid size measurements.