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Index >> Microbiological Methods >> Scanning Electron Microscopy - SEM

Scanning Electron Microscopy - SEM

	Scanning Electron Microscopy - SEM Scanning Electron Microscopy - SEM allows surfaces of objects to be seen in their natural state without staining. The specimen is put into the vacuum chamber and covered with a thin coating of gold to increase electrical conductivity and thus forms a less blurred image. The electron beam then sweeps across the object building an image line by line as in a TV Camera. As electrons strike the object, they knock loose showers of electrons that are captured by a detector to form the image. Magnifications with this microscopy are limited to about 75,000 -100,000 diameters.
The degree of magnification needed to observe a microbe depends upon its size Bacteria, fungi, algae, protozoa can be viewed with a light microscope. Smaller microorganisms, like viruses, as well as the internal structures of cells, require the use of electron microscope. The choice of a particular microscope depends upon the size of the object, the degree of detail that must be viewed, the nature of the specimen, and the overall purpose of the microscopic
Extensively used in microbiology, usually necessary to stain specimens for observation. Used for live microbes, particularly those with characteristic morphology, staining not required. Improved resolution over light microscope, largely replaced by electron microscopes. Flourescent staining used, useful in several diagnostic procedures for identifying microbes.
Used to examine structures of live microbes, produces sharp multi colored three-dimensional image. Used to view ultra structures of microbes, including viruses; much greater resolving power and magnification than light microscope. Used for detailed surface structures of microbes, produces a three dimensional image.

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