8/23/2016 Condenser contains an opaque Types of Light Types of Light Microscopy disk that eliminates all light in the center of the beam(light Microscopy that enters the lens directly) Dark-Field Many different types of light microscopy Only light reflected by the Bright-field specimen enters the objective lens Dark-field Light objects are visible against Fluorescence a dark backoround. Used to exomine: live microbes that have little contrast in bright-field microscopy that be microbes that are distorted by staining Types of Light Microscopy Types of Light Microscopy:Fluorescence Bright-Field Uses UV(ultra violet)light ·Usual operating Fluorescent substances absorb UV conditions of a light and emit visible light. compound light Cells may be stained with microscope fluorescent dyes:fluorochromes. ·Dark objects are A principle use in microbiology is a visible against a bright diagnostic technique called background. immunofluorescence A fluorescent antibody binds a ·Light reflected off specific microbe-labeling the the specimen does not enter the objective microbe with fluorescence Pathogenic microbes are detected orange lens. within clinical specimens8/23/2016 4 Types of Light Microscopy Many different types of light microscopy Bright-field Dark-field Fluorescence 13 • Usual operating conditions of a compound light microscope • Dark objects are visible against a bright background. • Light reflected off the specimen does not enter the objective lens. Types of Light Microscopy Bright-Field 14 Types of Light Microscopy Dark-Field • Condenser contains an opaque disk that eliminates all light in the center of the beam (light that enters the lens directly). • Only light reflected by the specimen enters the objective lens. • Light objects are visible against a dark background. • Used to examine: - live microbes that have little contrast in bright-field microscopy - microbes that cannot be stained - microbes that are distorted by staining 15 • Uses UV (ultra violet) light • Fluorescent substances absorb UV light and emit visible light. • Cells may be stained with fluorescent dyes: fluorochromes. • A principle use in microbiology is a diagnostic technique called immunofluorescence • A fluorescent antibody binds a specific microbe - labeling the microbe with fluorescence • Pathogenic microbes are detected within clinical specimens Types of Light Microscopy: Fluorescence A thin blood smear showing trypanosomes stained with acridine orange 16