Lecture 16-17 Culture media, Cultivation techniques, & Types of cultures Flashcards
Two broad classes of culture media
chemically defined and complex
Chemically defined
exact composition of pure chemicals used to formulate medium is known
Used for well characterized isolates in lab studies
chemically defined
Complex media (“rich” media)
exact chemical composition is poorly defined
Used as a non-specific medium for growing many organisms
rich media
Often naturally sourced components
rich media
Selective media
inhibits growth of unwanted organisms, supports growth of desired organisms
The dye that inhibits growth of Gram-positives and selects for the isolation of Gram-negatives
Brilliant Green (BG) agar
Enriched media
contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms
Fastidious organisms
organisms that cannot make certain nutrients and require them to be added to their medium
Commonly used to supply nutrients in various mediums
blood, serum, egg yolk
Used to grow a wide range of pathogens, particularly those that are more difficult to grow
enriched media
Differential media
contains compounds that allow groups of microorganisms to be visually distinguished by the appearance of the colony or the surrounding media
What basis does differential media use to show visual differences?
biochemical differences
Alpha hemolysis
indistinct zone of partial destruction
Beta hemolysis
clear, colorless zone appears
Gamme hemolysis
no apparent hemolytic activity or discoloration