High resolution SEM of bacterial virus T7.

High resolution "low-loss" scanning electron microscopy is a relatively new technique which permits an investigator to examine structures that were formerly visualized exclusively by transmission electron microscopy [1]. This paper presents some images of intact bacterial virus T7, viewed at the ultrastructural level. Due to the high resolution capibility of this technique, and the demanding physical prerequisites for visualization of the specimen, current specimen preparation techniques were modified in order to permit 1--2 nm resolution in surface mode. Using this method of microscopy, it is possible to view clearly this small bacteriophage (the smallest of the T-coliphages), adsorbed to its host bacterium, in a scanning mode at magnification (and resolution) comparable to TEM without resorting to the use of replicas, or reconstruction of a two-dimensional image.