B: Culture Media Flashcards
What is a broth
liquid media
What is a plate/slant
if media is solidified with agar
What is defined media
all components are known and added in precise amounts
What is comlpex media
contain undefined components that contain source of all required nutrients
What are common ingredients in complex media
yeast extract, beef extract, peptones (protein hydrosylate)
What does selective media favour?
growth of some bacteria and inhibit others. note: it may not kill them
What is an example of selective media, what does it contian
MacConkey agar contains nutirents but also bile salts and crystal violet which inhibit gowth of gram +ive
How can adding antibiotic to media be considered selective
only antibiotic resistant bacteria will grow
What is differential media
media distinguish btwn different bacteria based on differences in metabolism
Why is MacConkey agar a differential, on top of being selective, media?
contains lactose and a pH indicator that changes to red in acidic pH
What is a colony
clone of one cell growing on surface of solid medium
Describe the different colors that occur on MacConkey agar and why it happens
pink/red- colonies of gram bacteria that ferment lactose and produce acidic waste
colourless-others
What is enriched media
media used for growth of fastidious bacteria eg leuconstoc
Give an example of enriched media
blood agar, includes sheep’s blood. contains lots of nutrients and growth factors
Blood agar is also differential. Describe 3 types that occur
beta hemolysis; clear zone around a colony
alpha hemolysis; greenish zone around the colony
gamma hemoylsis; no hemolyis
