What is the purpose of the phenol red test?
Terms in this set (11)
- Carbohydrates (glucose, lactose, sucrose)- L & S (disaccharides) help fuel fermentation.
- Digested casein (protein: milk)- a substitute for peptone.
- Phenol Red- our pH indicator
What is phenol red used to indicate?
Terms in this set (15)
- Acquire PR broths
- Inoculate PR broths with MO
- Incubate at 37 C for 48 hrs
- Observe color change
Why is phenol red used in experiments?
Phenol red was used by Leonard Rowntree and John Geraghty in the phenolsulfonphthalein test to estimate the overall blood flow through the kidney in 1911. It was the first test of kidney function and was used for almost a century but is now obsolete. The test is based on the fact that phenol red is excreted almost entirely in the urine.
What makes phenol red turn yellow?
Principle: Phenol Red Fermentation medium contains peptone, phenol red (a pH indicator) and the carbohydrate to be tested. Phenol red is yellow at a pH < 6.8 and red at a pH of > 7.4, therefore if a bacterium ferments a sugar to acid a yellow color will develop. Additionally, phenol red tubes contain an inverted Durham tube.
What does the phenol red test determine?
The objective of the exercise is to determine which organisms can utilize each sugar. Phenol red is a pH indicator which turns yellow below a pH of 6.8 and fuchsia above a pH of 7.4. If the organism is able to utilize the carbohydrate, an acid by-product is created, which turns the media yellow.
What does a positive results in the phenol red mannitol broth look like?
If mannitol can be used, the microbe will accumulate acidic byproducts. In a positive test, the pH indicator in the medium changes color from its normal red to yellow, indicating acid production.
What does it mean when phenol red turns red?
A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λmax = 443 nm) to red (λmax = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
What does it mean when phenol red turns orange?
Additionally, phenol red tubes contain an inverted Durham tube. If a bacterium produces a gas during fermentation this tube will trap that gas a a bubble will be observed in the Durham tube. Sometimes an orange color will develop in the tube, this represents a pH > 6.8 and should not be considered positive.
What color is a positive lactose test?
Positive test result: Tubes must be lemon yellow to be considered positive for lactose or sucrose fermentation. Positive tests are recorded with an “A” for acid. Negative test result: Orange or red are considered negative for sugar fermentation.
Why does phenol red change color to yellow?
In solution at very low pH phenol red is colorless and exists as a zwitterion, containing both a negatively charged sulfate group and a positively charged ketone group. With an increase in pH (pKa=1.2) the excess proton in the ketone group is lost, resulting in a yellow color.
What color does phenol red turn when the solution is acidic?
Answer and Explanation: Phenol red is an example of a pH indicator, and it gives the yellow color in acidic solution and bright pink color in alkaline solution.
What is indicated if the phenol red glucose broth stays red throughout incubation?
What is indicated if the phenol red glucose broth stays red throughout incubation? All bacteria produce gas when they ferment. What is indicated by a color change of a phenol red glucose broth from red to yellow?
What does a yellow broth color indicate?
Glucose Broth with Durham Tubes Like MSA, this medium also contains the pH indicator, phenol red. If an organism is capable of fermenting the sugar glucose, then acidic byproducts are formed and the pH indicator turns yellow.
What causes PR broths to turn yellow?
A yellow result is a positive result, as PR is a pH detector, and if an organism ferments carbohydrate, it releases acid, lowering the pH and turning the PR yellow. If you observe the PR broth to be pink with no bubbles, what does it signify?
What color is phenol red at neutral pH?
Phenol red is red or orange around neutral pH.
What is the medium used for phenol red?
Imaging medium: Phenol red free medium (such as RPMI or DMEM), 10% fetal bovine serum, 2 mM glutamine, 25 mM HEPES, pH 7.4. Other cell types may require different media. Note that phenol red is a chromophore that will absorb light and thus decrease the effective illumination of a sample.
What is the advantage of barium contrast radiography?
An additional advantage of the latter technique is the differentiation between solid and liquid-phase emptying.
What is the tear aqueous layer?
Evaluating the tear aqueous layer, as relevant to contact lens wear:#N#•#N#Assessment of the tear aqueous layer and/or tear production using at least one clinical method (TMH, Schirmer test or phenol red thread test) before contact lens fitting is essential for identifying any potential aqueous deficiency, to allow appropriate management strategies to be instituted and to guide the lens fitting approach in suitable candidates.#N#•#N#The Schirmer test has limited discriminative capacity for milder states of tear insufficiency.#N#•#N#TMH has the advantage of being a noninvasive measure of tear volume that is useful in dry eye assessment and can also be quantified with the contact lenses in situ.
What is a p-nitrophenol probe?
p-Nitrophenol is a suitable probe for measuring CYP2El activity in different species, including humans. 70,71 Hydroxylation of p-nitrophenol results in the formation of 4-nitrocatechol which, in alkaline medium, has a strong yellow color. 71–73
What is the normal size of a Schirmer tear test?
Typically, 10–20 mm is considered borderline and greater than 20 mm is typically normal. The Schirmer tear test uses a 5 by 35 mm strip of filter paper to measure basic and reflex tear secretion when used without anaesthetic. In theory, it measures only basic secretion when used with anaesthetic.
How is the concentration of one indicator measured?
A similar principle can also be used with a reversible fluorescent indicator where the concentration of one indicator form is measured by its fluorescence rather than by the absorbance intensity. Light, typically in the blue or UV wavelength region, excites the fluorescent dye to emit longer-wavelength light.
Does phenol red help with fluorescence?
More importantly, phenol red can contribute to background and can even mark lysosomes in cells illuminated with near UV light. The important things are to keep cells supplied with energy (from media), growth factors (serum), and to avoid the negative effect of phenol red dye on fluorescence imaging.
What is the concentration of sodium chloride in mannitol salt agar?
A 7.5% sodium chloride concentration will result in the inhibition of species other than the Staphylococci.
What is the purpose of mannitol salt agar?
The primary purpose of mannitol salt agar is to determine or select bacteria that have the ability to grow in a high salt environment. If there is no growth after adding salt, it means that the microorganism is intolerant to salt. Usually, Staphylococci have the ability to tolerate salt concentration.
What side of the mannitol salt agar test is Staphylococcus aureus
Picture 1: Mannitol salt agar test as a part of a selective medium. On the left side grows Staphylococcus aureus and no growth took side on the right side. Image Source: ytimg.com. Picture 2: Mannitol salt agar test on three plates with corresponding results. Image Source: wp.com.
What does it mean when a colony is yellow?
Yellow colonies with yellow zones – It indicates the presence of Staphylococcus aureus. Red colonies with red zones/Colorless – it indicates the presence of organisms other than Staphylococcus aureus, usually the ones found naturally occurring in the human body such as Staphylococcus epidermidis (found on human skin).
How long to sterilize a dehydrated medium?
The medium has a concentration of 11.1 grams in every 100 ml of distilled water. Sterilize through autoclaving at a temperature of 121 degree Celsius for 15 minutes. Allow the medium to cool down.
Is mannitol salt a differential medium?
Mannitol salt agar is a selective and differential medium. It isolates and identifies Staphylococcus aureus. At the same time, it also encourages the growth of some types of bacteria while inhibiting the growth of others. (2, 5, 8, and 9)
Does Staphylococcus saprophyticus ferment mannitol?
Staphylococcus saprophyticus may have the ability to ferment mannitol. It produces yellow hallow around the colonies during mannitol salt agar test resembling with Staphylococcus aureus. Escherichia coli does not grow in the medium while Staphylococcus epidermidis has colorless to pink colonies.
Method
- Aseptically inoculate each test tube with the test microorganism using an inoculating needle or loop. Alternatively, inoculate each test tube with 1-2 drops of an 18- to 24-hour brain-heart infusio...
- Incubate tubes at 35-37°C for 18-24 hours.
- Check for color changes or formation of gas.
Result Interpretation
- I. Acid production: 1. Positive:After incubation the liquid in the tube turns yellow (indicated by the change in the color of the phenol red indicator). It indicates that there is drop in the pH because of the production of the acid by the fermentation of the carbohydrate (sugar) present in the media. 2. Negative:The tube containing medium will remain red, indicating the bacteria cannot ferment th…
Uses
- It is recommended to determine the fermentation reaction of carbohydrates for the differentiation of microorganisms.
- It is useful in identifying Gram negative bacilli, especially Enterobacteriaceae.
- It is recommended to determine the fermentation reaction of carbohydrates for the differentiation of microorganisms.
- It is useful in identifying Gram negative bacilli, especially Enterobacteriaceae.
Limitations
- Phenol Red Broth test is not intended for use in the diagnosis of disease or other conditions in humans.
- Due to nutritional variation, some strains may be encountered that grow poorly or fail to grow on this medium.
- The addition of some carbohydrates to the basal medium may result in an acid reaction. To e…
- Phenol Red Broth test is not intended for use in the diagnosis of disease or other conditions in humans.
- Due to nutritional variation, some strains may be encountered that grow poorly or fail to grow on this medium.
- The addition of some carbohydrates to the basal medium may result in an acid reaction. To ensure accuracy of interpretation, uninoculated control tubes and/or inoculated Phenol Red Broth Base contr...
Reference
- https://homepages.wmich.edu/~rossbach/bios312/LabProcedures/Biochem%20characteristi…
- www.himedialabs.com/TD/M054.pdf
- www.austincc.edu/microbugz/phenol_red_broth.php
- https://quizlet.com/56724336/phenol-red-broth-flash-cards/
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