Oxidation- Fermentation Medium (observation & interpretation) PH indicator Bromt
ID: 197041 • Letter: O
Question
Oxidation- Fermentation Medium (observation & interpretation) PH indicator Bromthymol Blue E. coli P aeruginosa A.faccalis 1.Some microbiologist recommend a pair of 0-F basal media (without carbohydrate) along with the carbohydrate media. Why do you think this is done? ANSWERED 2.All enterics are facultative anaerobes. That is they have both respiratory and fermentative enzymes. What color would you expect for organisms in O-F media inoculated a wih an enteric? 3. Suplpose that you examined your tubes after incubating, you noticed that the unsealed control contained slight yellowing at the top. Suppose further that pair #1 showed complete yellowing of both tubes and pair #2 and #3 showed slightly yellowing of the unsealed tube. Assuming all other tubes were green, what conclusion could you safely make? Which results.if any, are reliable? Why? Which results, if any, are not reliable? Why not?Explanation / Answer
Before getting straight to the point we should know what does oxidation fermentation test means.
The test was developed to differentiate between oxidative bacteria and fermentative bacteria. The oxidative bacteria under aerobic condition only will produce acid from carbohydrates whereas fermentative bacteria produces acid in both aerobic and anaerobic conditions.
The test has it's own working principle. The test organism is inoculated in two tubes of peptone agar medium which contains glucose or any other carbohydrate to carry out the reaction. One tube among the two will be sealed with a liquid parrafin. This is done so as to prevent diffusion of oxygen. When the inoculated organism will utilize carbohydrates it will be indicated by a color change. The medium will change color from green to yellow. If the test organism is fermentative, then the color change will be seen in both the tubes whereas if the cool change is seen in the open tube then the organism is oxidative.
Now, let's study the organisms mentioned above.
P. aeruginosa
Observation- color change is seen in opened tube. Medium changed color from green to yellow.
Interpretation- the bacteria utilize carbohydrates under aerobic respiration and produces a small amount of weak acids during Ken's cycle and glycolysis. The increased concentration of glucose enhances the production of weak avids to a level that can be detected using an indicator. In this case Bromthymol blue indicator was used.
A. faecalis
Observation- no color change.
Interpretation- the inoculated organism is a non fermenter that means it won't convert carbohydrate into acids.
E. coli
Observation- color change was seen in both the tubes
Interpretation- glucose is converted into weaker acids under both aerobic and anaerobic conditions. This indicates that the test organism is a fermentative bacteria.
Some microbiologist recommend test without carbohydrates. Well some prefer medium containing carbohydrates. Well, both are acceptable but under proper laboratory condition and requirements.
2. As explained above, species from Enterobacteriaaceae are fermentative anaerobes i.e., they will show color change from green to yellow in both the tubes.
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