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Starch
A large carbohydrate molecule with hundred or thousands of glucose subunits. Since starch is so big, bacteria can't use the valuable glucose molecules in it without first breaking it down.
What is the enzyme used in Starch Hydrolysis?
Amylase, which breaks (hydrolyzes) some of the bonds between glucose subunits. Which helps bacteria break down starch.
What is the medium used in the Starch Hydrolysis Test?
A Starch Agar plate, which is a standard agar plate with added starch. The starch is clear because it completely dissolves in water.
How can you see starch on the Starch Agar Plate?
You add Iodine to the plate after incubation. The Iodine forms a dark blue/black complex with starch but remains its original amber color in the absence of starch.
What does a positive Starch Hydrolysis test look like?
After incubation and the iodine is added the iodine will remain its original amber color around the bacteria that has the enzyme Amylase.
What does a negative Starch Hydrolysis test look like?
After incubation and the iodine is added the iodine will turn a dark blue/black complex with the starch that is intact.
What does a positive Starch Hydrolysis test mean?
It means that the bacteria has the enzyme amylase.
What does a negative Starch Hydrolysis test mean?
It means that the bacteria doesn't have the enzyme amylase.
What are the steps of a Starch Hydrolysis Test?
1) Use a loop to streak each organism in a single line on the surface of the Starch Agar Plate.
2) Incubate the plate at 37C till next class
3) Obtain the incubated plates
4) Coat the surface of each agar with Gram's Iodine
5) Observe and record
What is the reagent used?
Grams Iodine
