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38 Cards in this Set
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- Back
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define: complex media
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non-synthetic, non-defined and quite rich.
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What are some types of complex media?
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nutrient agar and tryticase soy agar
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What is nutrient agar?
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• Nutrient Agar is a complex media
• It is comprised of peptone (5 grams per liter of water), beef or yeast extract (3 grams per liter) and agar (15 grams per liter of water). |
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What is tryticase soy agar
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• another example of complex media
• trypsin (enzyme) is used to partially digest soy proteins. |
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define: synthetic media
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chemically defined media
• provides for consistency since all components are carefully measured out • media produced is not very rich • it may be difficult to get adequate growth with some organisms |
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What is an example of synthetic media?
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glucose-salt media
• It consists of inorganic components such as ammonium sulfate, calcium chloride, sodium phosphate, magnesium nitrate and potassium hypophosphate • To get growth an enormous number of additives may be necessary |
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define: semi-synthetic media
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media type where all components are carefully weighed out and measured and one more growth factor (not weighed or measured out) is added.
• added growth factors may include blood serum or blood plasma. • Plant pathogens grow when coconut milk is added |
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define: agar
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(complex polysaccharide) is used as a solidifying agent. Formerly used gelatin (protein)
• Agar is derived from sea weed (red algae). Terrestrial organisms and human pathogens are not very successful at breaking down agar. • Agar will remain solid and not break down when these organisms are used • Agar melts at 100 degrees C • organisms can be introduced at 50 degrees C and the agar will still be in liquid (molten) form |
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What is the technique for making pour plates out of agar?
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• organisms can be introduced at 50 degrees C and the agar will still be in liquid (molten) form
• The 50 degrees C temperature is not so high that the organisms will be killed • The organism can be introduced, mixed for equal distribution and pour into plates. • Agar is cooled and solidifies at 44 degrees. • Once agar is solidified, it must be heated to 100 degrees C for re-melting • We use 15 grams of agar per liter of water |
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What are some special media types?
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1. Selective media
2. Differential Media 3. Enriched Media 4. Enrichment Media 5. Anaerobic Media |
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define: Selective Media
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will promote the growth of organisms with the use of a favorable carbon source, and will reduce the growth of other organisms with the use of inhibitory substances
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What are some examples of Selective Media?
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a. Sabourauds Dextrose Agar
b. Phenylethyl Alcohol Agar |
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What is Sabourauds Dextrose Agar (SAB)?
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high concentrations of sugar promote yeast growth and inhibit bacterial growth. In addition, low pH also inhibits bacteria
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What is phenylethyl Alcohol Agar?
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(Phenylethanol Agar) Promotes the growth of gram positive cocci. Alcohol content tends to inhibit gram negative organisms
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What is Differential Media?
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will make it easier to distinguish colonies of the desired organisms from other colonies growing on the same plate. Differences can be observed
• Oftentimes, colors that develop as a result of unique biochemical reactions are observed |
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What color will Escherichia coli have if grown on Eosin Methylene Blue media?
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greenish metallic sheen
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What will happen if Streptococci are grown on Blood Agar?
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different species of Streptococcie will hemolyze the red blood cells in varying ways.
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What is alpha hemolysis?
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a partial breakdown of RBC's results in a partial clearing that has a greenish tinge
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What is beta hemolysis?
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a complete breakdown of RBC's or clearing occurs
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What is gamma hemolysis?
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no breakdown of RBC's of clearing occurs
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What beta hemolytic Streptococci is the most dangerous?
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Streptococcus pyogenes
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What type of agar can be used as an enrichment medium since it is very rich and supports the growth of fastidious organisms?
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Blood Agar
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What is de(s)oxycholate agar?
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a medium that is recognizes the presence of gram negative enteric organisms that ferment the milk sugar lactose
• produce a red pigment in the medium |
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What is enriched media?
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very rich medium designed to allow fastidious organisms to grow. Blood Agar is one example. Brain Heart Infusion (BHI) another enriched medium is a rare example of an infusion that is still used today
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What is enrichment media?
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provides nutrients and conditions that favor the growth of a particular microbe. (Selective media are used to isolate out groups of organisms).
• Enrichment media will promote growth and dominance of a sensitive organism from a mixed culture. • This media teases out the organism |
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What are some anaerobic media and conditions?
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a. candle jar - older technique where inoculated media and a lit candle were enclosed within a jar. Burning candle used oxygen and produced carbon dioxide to provide anaerobic conditions
b. Special reducing media where oxygen is chemically combined and taken out of the mixture is sometimes used. Thioglycollate Medium is an example of this type of media c. Hydrogen gas generation in an enclosed jar can also be used. The hydrogen combines with available oxygen and forms water. Commonly used in labs today. |
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What are the two types of pure cultures?
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axenic cultures and clones
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define: axenic cultures
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these cultures consist of single species, a monoculture, in an environment free of other species. These organisms are not genetically identical
• we use these in lab |
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define: clones
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these cultures consist of cell that are genetically identical. A close is derived from a single cell. Clone cultures will not be stable and remain as clones. These cultures of mutation and genetic recombination will eventually be axenic cultures
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What are some methods for isolating and obtaining pure cultures?
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plating, serial dilutions and single cell isolation
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What are some plating techniques?
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a. streak plates - most common method of plating
b. pour plates c. spread plates |
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What is the most common method of plating?
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streak plates
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What is serial dilutions?
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making dilutions until we end up with single cells. Lister's technique used to obtain pure cultures.
• serial dilutions can also be used to reduce the number of cell/mL for purposes of counting concentrated suspensions of bacteria |
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What is single cell isolation?
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use a micromanipulator to pick up a single cell
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Where do we get stock cultures from?
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nature, a clinical laboratory, or from culture collections
• the most famous is ATCC (American Type Culture Collection) |
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What are the types of ways we can maintain our cultures?
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periodic transfer or lyophilzation
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What is periodic transfer?
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can vary time, temperature, media and growth conditions
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What is lyophization?
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(cryodessication or Freeze Drying)
• this is the best way to store and preserve cultures |
