Exercise 7: chemically defined, complex, selective, and differential media
What do selective media allow you to do?
isolate certain bacteria even if they constitute only a small percentage of the population
What kinds of organisms does EMB agar differentiate?
lactose fermentors vs non-fermentors
Definition: selective medium
medium formulated to permit the growth of certain bacteria but not others
Definition: differential medium
medium permitting certain organisms to be distinguished from others by the appearance of their colonies
Which organisms that you tested do not required any growth factors
organisms that can grow on glucose salts
Definition: fastidious
organisms that require many complex nutritional supplements
What type of medium is trypticase soy agar?
rich, complex medium
What are complex media often called?
rick (enriched) media
What type of medium is Eosin Methylene Blue (EMB) agar?
selective (for gram-negative) and differential media (contains sugar lactose that certain organisms ferment)
What type of medium is glucose mineral agar
simple, chemically defined medium
What is the hockey stick tool used for?
spreading bacteria on spread plates
Which organisms that you tested cannot grow on glucose mineral medium?
staphylococcus
Why do complex media tend to support the growth of bacteria better?
they contain many preformed nutrients and the organisms don't have to use energy and material to synthesize the compounds supplied in the medium
How do lactose negative organisms appear on EMB plates?
white or light pink colonies
Which organisms could grow on glucose mineral medium?
E. coli, pseudomonas, enterobactor
Definition: Glucose mineral medium
a chemically defined medium containing glucose as a carbon sources and salts such as NH4Cl and KH2PO4 for a nitrogen and phosphate source
Definition: growth factor
a compound such as a vitamin or an amino acid that is required by an organism for growth
Definition: rich (or enriched) medium
a medium, usually complex, containing many growth factors; sometimes, blood or additoinal vitamins are added to permit the growth of organisms with special requirements
Definition: chemically defined medium
a synthetic medium composed of inorganic salts and usually a carbon source such as glucose
What is the purpose of selective medium?
allow some things to grow and not others
Definition: undefined medium
also termed a complex medium; a medium in which the exact amounts of chemical components and their composition are unknown because it is made of extracts or enzymatic digests of meat, plants, or yeast
Definition: complex medium
also termed an undefined medium; a medium in which the exact amounts of chemical components and their composition are unknown because it is made of extracts or enzymatic digests of meat, plants, or yeast
Definition: Enteric
associated with the intestine
What do differential medias allow you to determine about bacterial characteristics?
characteristics such as whether or not they can ferment certain sugars
Which media are the exact amounts and kinds of large organic molecules not known?
complex (undefined) medium
How do lactose positive organisms appear on EMB plates?
dark pink or purple colonies
What is the purpose of differential medium?
determine characteristics of something growing
Which organisms could ferment lactose?
e. coli and enterobactor
Which organisms could grow on the EMB plates?
e. coli, enterobactor, pseudomonas
What type of bacteria can grow on EMB plates?
gram-negative enteric rods
