Introduction and Background

The enzyme amylase is present in many living things, including bacteria, animals, and humans.  The enzyme breaks down the large polysaccharide starch into smaller portions which can be broken down by other enzymes.  The ability to produce amylase is not universal among bacteria, the best-known group of bacteria that can are found in the genus Bacillus.  To help identify amylase-producing bacteria, Petri dishes containing agar enriched with high amounts of starch are used.  Bacteria are grown on the agar and the plate is covered with Iodine after incubation.  The Iodine will react with the starch in the agar, causing the Iodine to turn a dark blue color.  After treatment with Iodine, the plates are examined for the following results:

  1. Positive for Amylase – A halo-like clearing will be present around the bacteria. The Iodine would be the normal yellow-brown color in these areas.
  2. Negative for Amylase – The entire area of the starch agar turns a dark blue color.

Please note that it is easy to be fooled by this experiment.  Sometimes the bacterial growth may look like a positive result when you look under the plate, but what is happening is that the Iodine cannot get underneath the bacterial growth and stain the agar.  Make sure you are looking on the edges of the bacterial growth for the halo-like clearings.

Laboratory Procedure

A typical procedure for this experiment would involve the following steps:

  1. Obtain the following materials:
    • One starch agar plate
    • Inoculation loop
    • Bacterial culture
  2. Inoculate the starch agar by taking one loopful of the bacterial culture and streaking across the surface of the agar in a zig-zag pattern.
  3. Label the bottom of the plate and incubate the plate for 2-3 days in the designated incubation area.
  4. After incubation, cover the entire area of agar with Iodine and wait about 5 minutes. After waiting, carefully examine the plate to determine results and do not let the Iodine spill from the plate.

Perform the following data analysis and submit the following answers to the questions below:

Organism Name

  1. ?? (need name)

2. Growth? (Y/N) 


3. Color of medium around colonies after Iodine

dark blue

Starch Hydrolysis? (Y/N)

(yes or no??)

Organism name?

  1. ?? (need name)

2. Growth? (Y/N)


3.Color of medium around colonies after Iodine


Starch Hydrolysis? (Y/N)


1. When Amylase breaks down starch, name one product of the reaction.

2. Members of the genus Bacillus are known to produce Amylase. What advantage might producing Amylase provide these bacteria?

All papers are written by ENL (US, UK, AUSTRALIA) writers with vast experience in the field. We perform a quality assessment on all orders before submitting them.

Do you have an urgent order?  We have more than enough writers who will ensure that your order is delivered on time. 

We provide plagiarism reports for all our custom written papers. All papers are written from scratch.

24/7 Customer Support

Contact us anytime, any day, via any means if you need any help. You can use the Live Chat, email, or our provided phone number anytime.

We will not disclose the nature of our services or any information you provide to a third party.

Assignment Help Services
Money-Back Guarantee

Get your money back if your paper is not delivered on time or if your instructions are not followed.

We Guarantee the Best Grades
Assignment Help Services