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What are the two different types of culture media?
solid or liquid
What is the purpose of a culture media?
- support growth of microorganisms
- provide nutrient requirements for specific bacteria
What are culture medias available as?
- dehydrated powder to prepare yourself
- prepared agar plates
- ready-to-use for biochemical tests
What nutrients does an agar typically contain?
- meat extract
- solidifying agent
What is a peptone?
What do peptones do?
provides amino acids and nitrogen
Are peptones needed for growth of the microorganism?
Are peptones an organic or inorganic salt?
What is the purpose of salt in the agar?
- adjusts the osmotic pressure
- isotonic for the bacterial cell
What is dextrose and why is it needed in the agar?
- dextro glucose
- source of carbon and energy
Why is water in the agar? What kind of water do we use?
- added to provide food material in a soluble form
- can be used by the bacteria
- used distilled water to ensure uniformity
What is the purpose of meat extract in the agar?
provides water soluble carbohydrates, nitrogen, and vitamins
What are the solidifying agents of an agar?
- dried extract of sea algae
- not attacked by bacteria
- melts at 42 degrees celcius
What are the solidifying agents of gelatin?
- animal tissue protein
- bacteria attack and liquefy it
- melts at 31 degrees celsius
- bacteria are usually incubated at 37 degrees celsius
What are the different types of media?
What is an enriched media?
basic nutrient media with added ingredients
What are some of the added ingredients for an enriched media?
What is a selective media?
- contains antibacterial substances
- inhibits or kills all but a few types of bacteria
- facilitates the isolation of a particular genus of bacteria from a mixed colony
What is a differential media?
- bacteria can be differentiated into groups
- differentiate due to the biochemical reaction on the medium
What is an enrichment media?
- liquid media
- favors growth of a particular group of organisms
- may contain inhibitory substances that suppress competitors
What is a synthetic media?
- prepared from pure chemical substances
- exact chemical composition is known
- used in experimental work
What is trypticase soy agar?
common basic medium - enriched
What does trypticase soy agar contain?
- enzymatic digests of casein and soybean meal
- dipotassium phosphate
What do we use the trypticase soy agar for?
- practicing streak technique
- to observe differences in colony morphology
- to perform the catalase test
What would you like to do?
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