Ammonium molybdate solution

Visualization of bacteriophages by transmission electron microscopy were based on the method described by Maszewska et al. [31 (link)]. The high titer bacteriophage lysates were centrifuged at 24500 g for 3 h at 4 °C. Then the phages were washed twice with 5% ammonium molybdate solution (Sigma-Aldrich) pH 6.0 using the above spin conditions. The final sediments were suspended in 5% ammonium molybdate to obtain the titer of 10¹¹ pfu ml^− 1. Subsequently, one drop of the phage suspension was placed onto the formvar and carbon coated 200-mesh copper grid (Polysciences, Inc., Warrington, USA) and drained for 3 min. Then samples were negatively stained for 45 s. with 2% (w/v) phosphotungstic acid (PTA) in darkness. The ultrastructure of bacteriophages was visualized by transmission electron microscopy (TEM) with the JEM 1010 electron microscope (JOEL Ltd., Tokyo, Japan) at 80 kV in the Laboratory of Microscopic Imaging and Specialized Biological Techniques of the Faculty of Biology and Environmental Protection, University of Lodz. To examine bacteriophages samples the magnification of 60,000 to 100,000 was used.