24 Tube Inoculating

We inoculated tubes containing sucrose, glucose, lactose or nutrient gelatin. The liquid tubes are to test carbohydrate utilization. These tubes also conatined a durham tube which is used to indicate gas production. The tubes all had Phenol-red as the ph indicator. This procedure is done to determine if a microbe is facultative, deriving it's energy from fermentation. The fermentation will result in acid production which will lower the pH of the broth and the broth will turn yellow. If not full yellow, the result is negative. Some organisms will also produce amonia and CO2. The durham tube will capture this any gas produced.
The gelatin tubes are to show gelatin hydolysis from the enzyme gelatinase. The protein gelatin is digested by some organisms. This test determines if the microbe does or does not produce gelatinase. If the organism does, the gelatin will change from solid to liquid.
We also made a Qudrant streak plate on Starch Agar and Tributyrin Agar streaked with E. coli, Bacillus subtilis and our unknown. Starch agar selects organisms that produce the enzyme amylase to break down starch. Starch hydrolysis is indicated by a clear zone due to the action of amylase.
Tributyrin Agar is used to show fat hydrolysis by the enzyme lipase. Organisms that can hydrolysize fat will have a clear zone around their colony.