Lab 20-23 Flashcards
Indole Test
Tests for use of tryptophan as a carbon/nitrogen/energy source.
Methyl Red/Voges Proskauer
Tests for acid production as an end product of glucose fermentation.
Citrate test
Sodium citrate for carbon/energy source. Bromothymol blue will turn from green to blue if citrate is used.
Indole Results
E. Coli : indole produced
Enterobacter cloacae : no
Klebsiella penumoniae : no
Methyl Red results
E. Coli : acid
Enterobacter cloacae : no
Klebsiella penumoniae : acid
VP Results
E. coli : No
Enterobacter cloacae : non acid produced (acetyl methyl carbon)
Klebsiella penumoniae : no
Citrate results
E. coli : no
Enterobacter cloacae : citrate used
Klebsiella penumoniae : citrate used
Test for H2S production
Tell between gram negative rods that do not ferment lactose
Peptone Iron Agar - PIA
Contain peptones for bacteria to use
Contains Iron for H2S indicator
IMViC Tests
Indole Production, methyl red test, Voges-Proskauer, citrate utilization
Sulfur Indole Motility (SIM)
Same ingredients as PIA, peptones and iron, plus tryptophan. Determines H2S production and motility.
Shigella Flexnerii PIA/SIM
H2S : no
Indole : no
Motile : no
Proteus vulgaris PIA/SIM
H2S : yes
Indole : yes
Motility : yes
Salmonella typhimurium PIA/SIM
H2S : yes
Indole : no
Motility : yes
Fermentation RXN
2 stages, glycolysis - 2ATP, fermentation- oxidizes NADH to be reused in another glycolysis
Fermentation Test Media
Specific sugar, phenol red (ph)
Carb fermentation results
No : red media/no bubble
Yes : yellow/no bubble
Yes/gas : yellow/bubble
Litmus Dye
pH indicator, can oxidation/reduction rxns
Role of milk/Lactose (acid production)
Litmus causes media to turn pink/red, if litmus milk reduced, tube is white at bottom with red color or ring at top.
Role of milk/lactose (curd formation)
Acid produced coagulates casein to form a curd, over time produce whey (liquid on top)
Role of lactose/milk (gas production)
Usually bubbles in curd, can produce lots of gas, causing curd to explode and forming “stormy fermentation”
Casein Coagulation: Hard Curd
Solid curd with lactose ferment/acid production. Acid causes curd to harden. Acidity increase causes whey to form on top if curd.
Casein Coagulation : Rennet Type Curd
Semi-soft curds in tube If bacteria can make Renin. Renin causes casein to form insoluble soft clot, usually formed at neutral pH
Casein Proteolysis : Peptonization
Gradual clearing of milk makes media transparent/clear.
Casein Proteolysis : Alkaline Reaction.
Casein breakdown yields lots of ammonia causing pH to become alkaline. Litmus dye causes media to turn purple/blue.
Litmus Milk Results : E. coli
Ac/AcG(not likely)
Litmus Milk Results : P. vulgaris
AlkP
Litmus Milk Results : B. cereus
AlkP
Litmus Milk Results : L. acidophilus
AcR
Litmus Milk Results : C. xerosis
No Change
What enzymes are needed for lactose fermentation?
Beta Galactosidase
What enzymes are needed for Casein Hydrolysis.
Renin.
Hard curd vs soft curd.
Hard : Lactose fermentation/acid production
Soft : Rennet type curd produced by Renin secretion at neutral pH.
