Selective Media

Notes from lab today 9/10/09

Selective Media: Agar that has ingredients that prevent growth of some bacteria, permit only certain kinda of bacteria to grow.
Ex. - Eosin and Methylene Blue prevent gram (+) bacteria growth
- Pseudomonas are gram (-)
- Streptococcus are gram (+)
Ex. - Manitol - Salt Agar has VERY HIGH concentration of salt
- Bacteria CAN live on this agar IF they can survive in salty environments
Ex. - Stapholococcus
- Bacteria that CANNOT live on this agar cannot survive in salty environments
Ex. - Streptococcus

Differential Media: Has ingredients that allow you to see metabolic differences between kinds of bacteria that grow on it.
Ex.- Manitol-Salt Agar: manitol is a sugar that some bacteria can ferment
Also include methyl-red = dye that changes red -> yellow at low pH
- Staph. Aureus CAN ferment and turns the agar yellow
- Staph. Epidemius CANNOT ferment the agar

My Personal Results:
-The bacteria from my hand plate did in deed grow on the MSA but doesn't ferment manitol
- Also it grew on the EMB so the bacteria is also gram (-)

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