High magnification scanning electron microscopy of bacterial cells and virions

When freeze-dried or critical point-dried cells of Escherichia coli and Bacillus sphaericus were coated with a 15 nm thick gold layer by means of sputtering, the surface of the bacteria appeared in the scanning electron microscope to consist of globules having a diameter of about 10–25nm. When the cells were coated with 3–5 nm of tungsten by sputtering, their surface appeared smooth or slightly grainy.Freeze-dried adenovirus type 2 virions sputtered with 15 nm gold exhibited an irregular surface, whereas virions sputtered with 3 nm tungsten looked smooth and had a more or less hexagonal shape. No capsomeres could be discerned.