Why are fermentation tubes evaluated at 24 and 48 hrs?
If an organism oxidatively metabolizes glucose, what will occur in the fermentation tubes?
Fermentation tubes are evaluated at 24 and 48 hours because these time points allow for the observation of different metabolic activities in microorganisms.
At 24 hours, the evaluation provides a preliminary assessment of the microorganism's ability to produce acid and gas from the fermentation of different sugars. This time point helps to determine the pattern and rate of carbohydrate metabolism by the organism.
At 48 hours, the evaluation is more comprehensive and allows for the detection of slow or delayed metabolic reactions. Some microorganisms may initially exhibit no significant metabolic activity at 24 hours but show positive results at 48 hours. This extended incubation period ensures accurate identification of the microorganism's carbohydrate fermentation capabilities.
Regarding your second question, if an organism oxidatively metabolizes glucose, it means that it can break down glucose in the presence of oxygen through cellular respiration. In this case, the organism will not produce acid or gas from the fermentation of glucose in the fermentation tubes. Instead, it will utilize the glucose aerobically, resulting in the production of carbon dioxide and water as by-products of cellular respiration. The fermentation tubes will show no visible changes, indicating a negative result for acid and gas production.