The purpose is to see if the microbe can use starch , a complex carbohydrate made from glucose , as a source of carbon and energy for growth. Use of starch is accomplished by an enzyme called alpha-amylase .<\/p>\n\n\n\n
A medium containing starch is used. After inoculation and overnight incubation, iodine reagent is added to detect the presence of starch. Iodine reagent complexes with starch to form a blue-black color in the culture medium. Clear halos surrounding colonies is indicative of their ability to digest the starch in the medium due to the presence of alpha-amylase .<\/p>\n\n\n\n
The medium used is starch agar<\/a> . The medium is a nutrient agar to which starch is added.<\/p>\n\n\n\n An inoculum from a pure culture is streaked on a sterile plate of starch agar<\/a>. The inoculated plate is incubated at 35-37 C for 24 hours. Iodine reagent is then added to flood the growth. Presence of clear halos surrounding colonies is positive for their ability to digest the starch and thus indicates presence of alpha-amylase .<\/p>\n\n\n\n Iodine reagent<\/a> is added after incubation to flood the surface of the plate.<\/p>\n\n\n\n 1. Select the starch agar<\/a> medium. <\/p>\n\n\n\n 2. Using an inoculating loop, complete the process of a tube-to-plate aseptic transfer<\/a> to inoculate the medium.<\/p>\n\n\n\n 3. Place the inoculated tube into the 35-37 C incubator. <\/p>\n\n\n\n 4. Press the New Day button<\/a> to move forward 24 hours.<\/p>\n\n\n\n 5. Incubate this test for only 24 hours. <\/p>\n\n\n\n 6. Retrieve the incubated culture from the incubator.<\/p>\n\n\n\n 7. This is a test that requires addition of reagents to bring about the change in appearance of a positive test. <\/p>\n\n\n\n Select the dropper tool and the appropriate reagent needed from the chemical shelf. For this test, select Iodine<\/a>. Remove the plate lid and add the reagent.<\/p>\n\n\n\n 8. Areas where starch has been digested by bacterial growth exhibit clear halos in the midst of the dark plate, indicating a positive alpha-amylase, or starch hydrolysis test. Plates containing bacteria without alpha-amylase are uniformly dark, a negative result. <\/p>\n\n\n\n 9.\u00a0Record test result<\/a>. \u00a0<\/p>\n\n\n\n Uninoculated:<\/a><\/p>\n\n\n\nHow is the test performed? <\/h3>\n\n\n\n
What reagents are added? <\/h3>\n\n\n\n
Performing this test in the VUMIE Online lab<\/h2>\n\n\n\n
Inoculation of Medium<\/h3>\n\n\n\n
Incubation of the Inoculated Medium<\/h3>\n\n\n\n
Addition of Reagents<\/h3>\n\n\n\n
Determination of Test Results<\/h3>\n\n\n\n