Basic electron microscopy of aquatic viruses
For high-resolution images, samples should be sterile and free from bacteria and other large particles.
Filter through membrane filters of 0.22–0.45 µm pore size.
Wash in a buffer, e.g., 0.1 M ammonium acetate (pH 7), in an ultracentrifuge with a fixed-angle rotor (25,000g or 25,000 rpm for 1 h).
Deposit a drop of virus suspension on a grid Leave for 30s for adsorption of viruses. 
Add a drop of stain. 
Withdraw liquid using filter paper. 
Operate transmission electron microscopes (TEMs) at 60–80 kV. 
Cool the object stage with liquid nitrogen to limit contamination by hydrocarbon molecules present in the column (and hence loss of resolution).
