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12 Cards in this Set
- Front
- Back
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• What is aseptic technique?
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o Transferring cultures from one medium to another without contamination is called aseptic technique. Performing procedure under sterile conditions. All items worked with need to be sterile (flaming loops/needles, sterile glassware, media, sanitizing work space, wearing gloves)
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• What is cultivation of bacteria? (culture)
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o Simply helping bacteria grow, by creating a culture. Conditions are provided that allow the bacteria to multiply in a controlled laboratory environment, and this is what makes up the culture.
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• What is a pure culture?
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o A pure culture consists of a single type of microbe of interest; it is free of contaminants; all descendants are from a single individual.
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• Difference between media: agar, liquid/broth, semisolid, and how they are used
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o Media is what is used to grow a culture of bacteria. It can be solid, liquid, or semi-solid
o Agar is an extract from marine red algae. When added to growth medium, the medium becomes solid. Often seen as a plate or slant to provide more area for growth. Concentration of agar will determine consistency of the medium. Agar becomes solid at temps below 40C. o Liquid or broth media is a liquid that stays liquid and does not solidify, from which bacteria gathers nutrients. Used for serial dilutions. Bacterial growth is present- will turn turbid. o Semi-solid media have smaller agar content. Inoculated by stabbing inoculating needle. used to test motility…non motile bacteria grow along stab, motile bacteria will swim, making the whole tube turbid. Also identifies oxygen requirements. Deeps. o Solid media are cooled on a slant to provide more area for growth at the medium-air interface. Petri dishes provide large surface area for isolating and observing colonies with naked eye. |
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• What is an autoclave? How does it sterilize things?
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o After media have been prepared, must be sterilized before use, usually in steam autoclave. The medium is heated to 121C at 15 psi for 15 min. This is sufficient to kill microbes, but spores require longer time- 30 min
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• Difference between chemically defined (synthetic media) and complex media
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o chemically defined (synthetic) media- prepared from purified ingredients, so its exact composition is known; must be used when you know exact growth requirements of the microorganism.
o Complex media- is that with any component not chemically definable. (can contain partially digested proteins- peptones- or bovine rbc’s |
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• Define the following: turbid, flocculent, pellicle, and sediment
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o Turbid- bacterial growth is present- will turn cloudy/brown
o flocculent- if there are clumps of microbial cells o pellicle- if there is membrane over surface of broth o sediment- sediment of microbial cells at bottom of tube |
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• Know how to streak a plate
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o Bacteria are pulled across Petri plate using sterile loop in series of streaks until individual bacteria are separated. Each bacterium will then grow into colony of identical cells that can be grown as pure culture.
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• What is differential media?
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o colonies may be different colors based off of biochemical properties; can differentiate between closely related organisms or groups of organisms
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• What is selective media?
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o inhibits growth of certain bacterial species. and allows the growth of others
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• Know how MSA is selective and differential; how colonies look
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o MSA- selective- allows gram positive growth, inhibits gram negative, because high salt concentrations inhibit growth of most organisms
o MSA- differential- differentiates between organisms that ferment Mannitol into acid-pH indicator turns red to yellow. Colonies that ferment mannitol will appear yellow because of acid production. |
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• Know how EMB is selective and differential; how colonies look
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o EMB- selective- allows gram negative. inhibits gram positive.
o EMB- differential- differentiates between lactose fermenting and non lactose fermenting bacteria. Two indicator dyes- eosin and methylene blue. lactose fermenters have dark colonies with clear borders. non-lactose fermenters have colorless colonies- E.coli has metallic green sheen because of acid production |
