A portion of the exercise will be used to determine if carbohydrate is oxidatively or fermentatively utilized. oxidation-fermentation agar containing a specific carbohydrate and bromthymol blue as the pH indicator will be used. This indicator is blue at pH 6.8 and yellow at pH 5.2. Mineral oil, vaspar or another similar material is used before incubation to layer media to show carbohydrate fermentation.