culture media and enumerating (A)
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Created by:
kjordan9097 on November 8, 2011
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10 terms
Terms | Definitions |
|---|---|
 Culture Media | -must contain substances to provide energy & C, N, S, P and growth factors -must be sterile to avoid unwanted microbes -agar in media from algae (complex polysaccharide to solidify) |
| Chemically Defined Media | The exact composition of media is known |
| Complex Media | Exact composition varies from batch to batch -usually contains extracts of beef, yeast or plants to supply a majority of energy, C, N & S requirements in the form of protein |
| Anaerobic Growth Media | Special reducing media is used so oxygen doesn't kill anaerobes -media contains ingredients combined with dissolved oxygen to deplete oxygen in media -ie: Anaerobic Jar (for oxygen-free petri growth) |
| Selective Media | Suppress growth of unwanted microbes and encourages growth of desired organism -ie: Sabourauds glucose agar- ph 5-6, selects for fungi |
| Differential Media | Used to distinguish desired organisms from others growing on plate -ie: Eosin Methylene Blue Agar -& MacConkey Agar (contains bile salts and crystal violet, inhibits growth of gram + bacteria) |
| Measuring Microbial Growth | 1) Direct Microscopic Count- counted in field of vision under microscope, then averaged 2) Standard Plate Count- serial dilution of suspension is prepared, poured into plates & grown, each colony represents 1 cell. Most frequently used method. |
| Filtration | To detect a low number of bacteria, like in lakes/streams -pass through filter, bacteria caught and incubated -used to detect coliform bacteria in water-fecal contamination |
| Most Probable Number (MPN) | Statistical method of estimating bacterial numbers -used in food and water sanitation evaluations |
| Turbidity | As bacteria multiply in liquid media becomes cloudy -Spectrophotometer used to judge light passing through bacterial suspension -Transmittance is the amount of light passing through media |
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