Presentation on theme: "Laboratory Tools in Microbiology"— Presentation transcript:
1 Laboratory Tools in Microbiology LECTURES INMICROBIOLOGYLaboratory Tools in MicrobiologyLESSON 3Sofronio AgustinProfessor
2 Topics Covered Microscopy Staining Techniques Methods of Culturing Microbes
3 Units of Measurement 1 µm = 10-6 m = 10-3 mm 1 nm = 10-9 m = 10-6 mm
4 Simple MicroscopeA simple microscope has only one lens
5 Parts of a student laboratory microscope Compound MicroscopeA compound microscope has two sets of lenses and is typically used in teaching and research laboratories.Parts of a student laboratory microscope
6 Optics : Magnification A specimen is magnified as light passes through the objective and ocular lenses.Total Magnification =objective lens X ocular lens(magnifications)The pathway of light and two stages of magnification of a compound microscope.
7 Resolution distinguishes magnified objects clearly. Optics: ResolutionResolution is the ability of the lenses to distinguish two points.A microscope with a resolving power of 0.2 um can distinguish between two points > 0.2 um.Resolution distinguishes magnified objects clearly.
8 Optics: ResolutionResolution can be increased by using immersion oil and shorter wavelengths of light.
9 Optics: RefractionRefractive index is the light-bending ability of a medium.The light may bend in air so much that it misses the small high-magnification lens.Immersion oil is used to keep light from bending.
10 Brightfield Microscopy Dark objects are visible against light background.Used to observe stained or unstained specimens.Most commonly used in laboratories.
11 Darkfield MicroscopyLight objects are visible against a dark background.Light reflected off the specimen enters the objective lens.Used to screen for syphilis agent, Treponema pallidum.
12 Phase-contrast Microscopy Accentuates diffraction of light that passes through the specimen.Used to observe internal cellular detail of live specimens.
13 Differential Interference Contrast (DIC) Microscopy Accentuates diffraction of light that passes through the specimen.Uses two beams of light to produce more pronounced contrast.
14 Fluorescence Microscopy Cells are stained with fluorescent dyes called fluorochromes.Uses UV light as energy source.Fluorochromes absorb UV light and emit visible lightFluorescent staining of fresh sample of cheek scrapings
15 Confocal Microscopy Uses fluorochromes and laser light. The laser illuminates each plane in a specimen to produce a 3-D image.
16 Electron Microscopy Very high magnification of up to 100,000 X. Transmission electron microscope (TEM)View internal structures of cellsScanning electron microscope (SEM)Three-dimensional images
17 Transmission Electron Microscopy Transmission Electron Micrograph of (a) a virus and (b) a protozoan.
18 Scanning Electron Microscopy False-color Scanning Electron Micrograph of Paramecium sp.
29 Simple Stain Use of a single basic dye is called a simple stain. A mordant may be used to hold the stain or coat the specimen to enlarge it.
30 Differential Stain: Gram Stain The Gram stain classifies bacteria into gram-positive and gram-negative.Gram-positive bacteria tend to be killed by penicillin and detergents.Gram-negative bacteria are more resistant to antibiotics.
33 Differential Stain: Acid Fast Stain Cells that retain a basic stain in the presence of acid-alcohol are called acid-fast.Non–acid-fast cells lose the basic stain when rinsed with acid-alcohol, and are usually counterstained (with a different color basic stain) to see them.
34 Culture of MicrobesFive basic techniquesMediaMicrobial growth