Wk2 lab. notes Flashcards
Selective media
permits growth of one organism and inhibit growth of another
Differential media
Indicate if certain organisms can carry out biochemical reactions: observable by diff. colour change
Enrichment media
Enhance growth of certain micro-o, especially if there is small no. of them
Combination selective and differential media
Permits growth of one and inhibits growth of another. AND assess if cerain micro-o undergo biochem. reactions
What type of media is McConkey agar (MAC)
Selective & differential medium.
- Selective for GNB: crystal violet, bile salts =inhibits growth of GPos. bact.
Diff: lactose fermenters = media turns red/pink (becomes acidic)
What type of media is Mannitol salt agar (MSA)
Selective & differential medium.
- Sel: detect staphylococci but not other bc Hi [salt] w/ some exceptions
- Diff: S. aureus & S. saprophyticus ferment mannitol (sugar) = produce acid = red -> yellow
What type of media is Blood Agar (BA)
Enriched media. Grow various organisms and can detect haemolysis. Detect streptococci
What would the morphology proteus vulgaris be?
Swarming bc it is motile = spread across surface of agar plate
Why do Gram neg. bact stain pink? link w/ theory of staining
gram neg bact. have thin peptidoglycan layer compared to gram pos. Crystal violet-iodine complex is formed (from crystal violet & Lugol’s iodine) which gets stuck in the thick peptidoglycan layer in Gpos once alcohol is added, so it washes off in Gneg bc CW is thin. Carbol fuschin stain Gneg pink
why doesn’t Gpos decolourise w/ alcohol. link w/ theory of staining
crystal violet-iodine complex gets stuck in thick peptidoglycan layer once it is washed w/ alcohol
Which organisms are able to grow in MAC?
Gram neg bact (E.coli) & proteus vulgaris
Which organisms are able to grow in MSA?
Staphylococcus aureus (ferment mannitol (sugar) = produce acid = red -> yellow)
