MMG 301 1nd Edition Lecture 2Outline of Last Lecture I. Introduction to microbiologyOutline of Current Lecture II. MicroscopesIII. Interaction of light with matterCurrent Lecture-microscopes-light microscope: uses glass lenses; maximum resolution 0.2 micrometers-electron microscope: uses electromagnets; maximum resolution 0.2 nanometers-interaction of light with matter-transmission: light goes through without being altered-absorption: object absorbs part of the light; energy level in the object increased-reflection: light bounces off the surface-refraction: light bends when it enters an object that alters its speed-scattering: some of the light is scattered in all directions-bright field microscope: the image results from light transmission through the sample and light absorption by some cell constituents-poor contrast-oil immersion lense increases resolving power-dark field microscopy: shows bright objects against a dark background-good for very thin or small specimens-phase contrast microscopy: provides increased contrast between bacteria and viewing mediumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-ideal to examine cell morphology-fluorescence microscopy: fluorescent cell appear colored against a dark background-staining techniques (to improve contrast)-simple stain: single stain, all objects are the same color-differential stain: multiple stains to distinguish between organisms-gram stain: allows detection of bacteria associated with host cells-positive: purple-negative: pink-acid-fast stain: differentiates mycobacteria from other bacteria-electron microscopy: uses an electron beam and magnets-used to study cell ultrastructures-transmission electron microscopy: sample is embedded in a polymer thin-section stain with heavy metal salts-shows external coats, cell envelope, internal structures, cell surface texture, and very thin external
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