Contrast development
In order to demonstrate the cellular and subcellular components, the basic anatomy and intracellular developments of microorganisms, some form of contrast enhancement is essential (21). Chemistry speaking, biological materials are composed mainly of the elements carbon, nitrogen, oxygen and hydrogen. These elements have low electron scattering power. Embedding materials have also a similar property and due to this, when sections are seen under electron microscope, hardly any contrast is observed which in turn results into a poor quality of image production. Techniques are now available to increase selectively the electron opacity of the specimen and thus enchanced image contrast.
