Lab Isolation Streak Flashcards
What are chemically defined (synthetic) media?
Media where the exact chemical composition is known and ingredients are typically salts
Useful for determining the nutritional growth requirements of microbes
What is general purpose (complex or rich) media?
Media where the exact chemical composition is not known; used to grow a wide variety of microbes
Key indicators include the use of digests, tryptone, and extracts
What is differential media?
Classification of grouping of microbes based on their ability to utilize nutrients and/or change colony appearance
Examples include blood agar, Methylene blue agar, MacConkey agar, and Mannitol salt agar
What does enrichment media do?
Encourages growth of some organisms while omitting selective pressure on others
Uses blood or serum to support the growth of fastidious organisms
What is selective media?
Media that actively selects against some species by containing ingredients that limit growth
Examples include MSA, EMB, and MAC
What is the selective interpretation of EMB and MAC?
Both are selective for gram negatives; they allow growth of gram-negative bacteria
MSA is selective for halophiles, allowing growth in high salt concentrations
What is the differential interpretation of EMB?
Identifies bacteria based on ability to ferment lactose; metallic green/pink/purple/black colonies indicate fermentation
Colorless colonies mean no fermentation
What is the differential interpretation of MAC?
Identifies bacteria based on ability to ferment lactose; pink colonies indicate fermentation
Colorless colonies mean no fermentation
What does a yellow ring around the agar in MSA indicate?
Mannitol has been fermented
No change in media indicates no fermentation
What is the streak plate technique?
Transferring an organism onto another solid medium to dilute the number of cells
It is used to isolate a pure strain from a mixture
