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Microbiology Ch. 4
Laboratory Methods
| Term | Definition |
|---|---|
| General principles of microscopy | wavelength of radiation magnification resolution contrast |
| magnification | an object is magnified in size so that it becomes visible to the observer |
| resolving power (resolution) | the ability to see fine details to resolve 2 separate objects as distinct structures |
| Total magnification of the final image | a product of the separate magnifying powers of the two lenses -- power of objective x power of ocular= total magnification |
| Contrast | -differences in intensity between two objects or between an object and a background -importance in determining resolution |
| What increases contrast? | staining use of light that is in phase |
| Compound microscopes | - series of lenses for magnification -light passes through specimen into objective lens -oil immersion lens increase resolution -have 1/2 ocular lens -most have condenser lens |
| Total magnifaction= | magnification of objective lens x magnification of ocular lens |
| Bright-field | most widely used, specimen is darker than surrounding field |
| Dark-field | brightly illuminated specimens surrounded by dark field |
| Phase-control | transforms subtle changes in light waves passing through the specimen into differences in light intensity, best for observing intracellular structures, very detailed viewing |
| Flourescent microscope | -direct UV light source at specimen -specimen radiates energy back as a longer visible wavelength -UV light increases resolution and contrast -some cells are naturally fluorescent; others are stained with fluorescent dyes -used to identify pathogens a |
| Confocal microscope | -use fluorescent dyes -use uv lasers to illuminate fluorescent chemicals in a single plane -computer constructs 3D image from digitalized image |
| Electron microscope | -greater resolving power and magnification -magnifies 10000x to 100000x -detailed images of bacteria, viruses, internal cellular structures, molecules, and large atoms |
| 2 types of electron microscopes | transmission and scanning |
| Staining | -increases contrast and resolution by coloring specimens with stains and dyes -smears of microorganisms (thin film) made prior to staining |
| Examples of stains | Gram, acid-fast, endospore, capsule, flagellar |
| Culture | visible (macroscopic) growth of organisms in or on a medium |
| Colony | macroscopic cluster of cells appearing on a solid surface; each arising from a single cell |
| Pure culture | contains a single specimen |
| Mixed culture | contains more than one specimen -when you know that you will have more than one species |
| Contaminated culture | contains "unwanted" species |
| Media can be classified according to 3 properties | physical state chemical composition functional type |
| Physical state | liquid, semisolid, and solid |
| Chemical composition | synthetic (chemically defined) and nonsynthetic (complex) |
| Functional type | general purpose, enriched, selective, differential, anaerobic, transport, assay, enumeration |
| Liquid | broth; does not solidify |
| Semisolid | viscous consistency; contains some solidifying agent |
| Solid | firm surface for colony formation -contains solidifying agent |
| Agar | -solidifying agent -a complex polysaccharide isolated from red algae -solid at room temp, liquefies at 100C, does not resolidify until it cools to 42C -provides framework to hold moisture and nutrients -not digestible for most microbes |
| Fastidious | bacteria that require growth factors and complex nutrients |
| Inoculation | introducing microorganisms into culture medium |
| Incubation | providing a controlled environment for culturing (grows best at 37C) |
| Identification of microbes | -biochemical assays -immune assays- can distinguish diff strands -nucleic acid fingerprints |
Created by:
KatelynnJoy
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