Generally speaking, fluorescence microscopy is very similar to ultraviolet microscopy. Fluorescence microscopy is based on the property of some substances to produce fluorescence right after have absorbed ultraviolet energy. In microbiology, the microorganisms can be stained with a fluorescent dye, like fluorochrome, in order to produce fluorescent images through UV microscope.

The main application of fluorescence microscopy in microbiology is the technique of identification of immunological reactions, I mean, of antigen-antibody reactions. The fluorochrome couples with the antibody and makes it possible to identify single cells which react with the antibody, through the emission of fluorescence. This technique is called immunofluorescence.

In immunofluorescence, a culture of bacterial cells is incubated with an antibody, which is coupled with a fluorescent dye. This dye-coupled antibody will cover the surface of some cells, while others will remain without the coupled. With the use of ultraviolet light, just the cells covered with the dye-coupled antibody will produce fluorescence and will look shiny at the microscope.

Next article: phase-contrast microscopy