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Why isn't a pH indicator needed in the lactose broth fermentation tubes?
A pH indicator is not needed in lactose broth fermentation tubes because the fermentation of lactose by bacteria produces acid as a byproduct, lowering the pH of the broth. This drop in pH can be visually observed as a color change in the medium, indicating lactose fermentation.
Why isn't a pH indicator needed in lactose broth fermentation tubes for detecting coliform bacteria?
A pH indicator is not needed in lactose broth fermentation tubes for detecting coliform bacteria because the presence of coliforms is indicated by gas production from lactose fermentation rather than pH changes. Coliform bacteria, such as E. coli, ferment lactose, producing acid and gas; however, the gas bubbles trapped in the inverted Durham tube provide a clear, direct visual cue of fermentation. The focus is on the gas indicator rather than pH changes, simplifying the detection process.
What is the Difference between single strength lactose broth and double strength lactose broth?
Single strength lactose broth contains a standard concentration of nutrients and lactose, typically used for cultivating organisms that ferment lactose, such as coliform bacteria. In contrast, double strength lactose broth has a higher concentration of nutrients and lactose, which allows for more robust growth and is often used when a greater degree of sensitivity is required in testing for lactose fermentation. The increased strength in double strength broth can enhance the detection of lactose fermenters in a sample.
When using the phenol red carbohydrate broth fermentation test at what pH is the pH indicator yellow?
The pH indicator phenol red turns yellow in the fermentation test when the pH drops below 6.8, indicating acid production from fermentation.
What reaction would you predict from an organism growing in litmus milk that has the following results in other media?
Assuming that you are asking about other media such as milk agar, PR lactose broth, purple lactose broth, and PR glucose broth, the answer you are looking for is as follows: A. A clear zone around the growth on a milk agar plate: indicates hydrolysis of casein, so should be clarification of medium present B. A/- in PR lactose broth: indicates lactose fermentation with acid and no gas produced, so should be pink litmus with acid clots and reduction of litmus in lower portion of medium C. A/G in purple lactose broth: indicates lactose fermentation with acid and gas produced, so should have pink litmus on top, acid clot, reduction of litmus, and fissures in the clot D. K in PR glucose broth: indicates peptone degradation with alkaline end products, so litmus should be blue
What is use double strength lactose broth?
Double strength lactose broth is used to selectively culture lactose fermenting bacteria. It contains a higher concentration of lactose compared to regular lactose broth, allowing for more efficient differentiation of lactose fermenters from non-fermenters based on acid production. This medium is often used in microbiology laboratories for various tests and experiments.
What culture media can be used to test the carbohydrate fermentation?
To test carbohydrate fermentation, common culture media include phenol red broth and MacConkey agar. Phenol red broth contains a specific carbohydrate, and the color change indicates fermentation. MacConkey agar is selective for Gram-negative bacteria and differentiates lactose fermenters, which produce acid, leading to a color change in the medium. Both media are effective for assessing the fermentation capabilities of various microorganisms.
Why in presumptive test only lactose broth is used not glucose broth?
In presumptive tests for coliforms, lactose broth is preferred over glucose broth because many coliforms can ferment lactose, producing gas and acid, which are indicators of their presence. While glucose can also be fermented by some bacteria, it is less specific for coliforms. The use of lactose broth helps ensure that the test is more selective for lactose-fermenting organisms, making it a better choice for detecting coliforms in water and food samples.
What are the essential ingredients of a carbohydrate broth?
nutrient broth + 0.5% particular carbohydrate + indicator
Why do you need to have an impeller in fermentor?
To mixed the culture broth during fermentation
Composition of double strength lactose broth?
Double strength lactose broth typically contains peptone, yeast extract, lactose, and possibly other nutrients or supplements. It is commonly used for the cultivation of coliform bacteria, such as E. coli, in microbiology labs.
Saline lactose broth sterilization method?
If the broth contains only saline and lactose, it can be autoclaved. However, it it contains peptide growth factors depending on the application, it will have to be filtered prior to use since protein-containing media is sensitive to heat.
