Microscopy

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Microscopy

Microscopy
Since the discovery of lens and compound microscope in the 16th century and microorganisms by Antoine van Leeuwenhoek (1632-1723), several types of microscopes have been commercially made available.

These instruments can provide structural details of microorganisms that are beyond the reach of the unaided human eye. Two features of microscopes are related to magnification and resolution limit provided by the lenses or lens systems used.

A. The Formation of Plaques	B. Electron micrograph of Escherichia coli	C. Electron micrograph of negatively stained particle

Magnification of an object results in the multiplication effect of the overall dimensions of the objects viewed. The resolution limit of a lens (or lens system) is the smallest distance by which two points can be separated and still be seen as distinct points; blurred image results when this resolution limit becomes less because the two points merge and

A. Bacteriophage	B. Diagram of a bacteriophage before injection	C. Diagram of a bacteriophage after injection

Conditional and Restricted Lysis

appear as a single point. The naked human eye has a resolution limit of approximately 0.1 mm and therefore structural details with distances of less than 0.1 mm cannot be resolved by the eye.

Magnifying lenses or microscopes have a resolution limit less than that of the eye and enlarge the details of the subject being examined and thus improve the eye's resolution limit. For instance, if two points are 0.5 m m (0.0005 mm) apart, a lens system with a resolution limit not greater than 0.5 m m may be needed to see the two points distinctly.

To achieve this resolution limit, the lens system must magnify the image delivered to the eye atleast 200 times so that the two points are apart by 0.1 mm or higher (200 x 0.0005 mm = 0.1 mm). This magnification comes close to or above the natural resolution limit of the naked eye.

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Algae Protozoa of Microorganisms Bacteriophges Fungal Viruses Microscopy Compound Light Microscope Bright Field Microscope Dark Field Microscope Fluorescence Microscope Ultraviolet-UV Microscope Phase Contrast Microscope Electron Microscope (EM)

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