Microorganism Lab Report

Purpose:

To identify an unknown microorganism by performing a series of biochemical tests on a pure bacterial culture.

Materials and Methods:

1. Carbohydrate Utilization: Two culture tubes, phenol red lactose broth and phenol red sucrose broth, were each inoculated with one loopful of organism 3 from a broth culture. The broths were incubated at 37°C. After 24-48 hours, the mediums were examined. A positive test result is indicated by a change from the red broth to a yellow broth. A change from red broth to orange broth, or no change in color, is indicated as a negative result. A gas bubble produced in the Durham tube is indicated as a positive result for gas. A negative result for gas is indicated by no gas in the Durham tube.

Casein Hydrolysis: The skim milk agar plate did not have any clearing around the growth. This is a negative test result.

8. Catalase Production: When 3% hydrogen peroxide was added to an isolated colony, no bubbles formed. This is a negative test result.

Discussion:

1. Carbohydrate Utilization: The test result for the phenol red lactose broth was positive for acid and negative for gas. The positive result for the acid means that the organism is able to ferment the particular sugar lactose. The Durham tube did have gas in it which means the organism produced gas in the lactose broth. The rest result for the phenol red sucrose broth was negative for both acid and gas. This means the organism was not able to ferment in sucrose. The organism was also not able to produce gas in the sucrose broth.

2. Indole Production: The result for this test was negative. This means the organism does not produce tryptophanase. The organism is not able to split the amino acid tryptophan into indole and pyruvic acid. There was no indole produced from the breakdown of tryptophan.

3. Urea Hydrolysis: This test result was negative. There was no accumulation of sufficient ammonia from the hydrolysis of urea. An alkaline environment was not created by organism