Unit 9 Carbohydrate Fermentation Durham Tubes

Summary

The video explains the process of testing carbohydrate fermentation in microorganisms using Durham tubes. These tubes contain phenol red as an indicator, which turns yellow when acid is produced during fermentation, signaling the presence of specific enzymes. The inverted glass tube inside the Durham tube is used to detect gas production. The video demonstrates how different colors indicate whether an organism can ferment sugars like lactose or sucrose, and how this test can be used alongside others like TSI to identify an organism's metabolic capabilities.

Takeaways

• 🔬 The video discusses the fermentation of simple sugars using Durham tubes, a method to test an organism's ability to ferment specific sugars.
• 🌡️ Durham tubes contain an inverted glass tube to capture air bubbles, indicating gas production during fermentation.
• 🍬 The presence of different sugars in separate tubes allows for testing an organism's ability to ferment various simple sugars.
• 🧬 An organism's ability to ferment a sugar suggests it possesses the necessary enzymes, such as lactase for lactose or sucrase for sucrose.
• 🌈 Phenol red is used as an indicator in the broth; it turns yellow if the pH drops due to acid production from fermentation.
• 🟡 A yellow color in the Durham tube indicates a positive result, showing that the organism can ferment the sugar and produce acid.
• 🔴 A red or orange color suggests a negative result, meaning the organism lacks the enzyme to ferment the specific sugar.
• 💨 The clearing of the inverted glass tube indicates the production of CO2, which is associated with acid production and fermentation.
• 🔍 Observing air bubbles in the inverted tube is crucial, as a significant amount of clearing (at least a third of the tube) is needed to confirm gas production.
• 📚 Using Durham tubes in conjunction with other tests like TSI can provide comprehensive information about an organism's carbohydrate fermentation capabilities.

Q & A

What is the purpose of the Durham tube in microbiology?

The Durham tube is used to test the fermentation of simple sugars by microorganisms. It contains an inverted glass tube to catch air bubbles, indicating gas production during fermentation.

How does the inverted glass tube inside the Durham tube function?

The inverted glass tube is used to capture air bubbles produced during fermentation. If the tube is cleared by at least a third, it indicates that the organism can produce CO2 as a byproduct of fermentation.

What role does phenol red play in the Durham tube?

Phenol red is an indicator in the Durham tube that changes color based on pH. It starts red and turns yellow if the pH drops due to acid production, indicating fermentation.

What color change in phenol red indicates acid production during fermentation?

A color change from red to yellow in phenol red indicates acid production, suggesting that the organism can ferment the sugar and produce an acidic byproduct.

What color of phenol red suggests that the organism does not ferment a particular sugar?

If phenol red remains orange or red, it indicates that the organism does not have the enzyme necessary to ferment the sugar, and no acid production has occurred.

How can you determine if an organism has the enzyme to ferment lactose based on the Durham tube test?

If the phenol red in the lactose tube turns yellow and the inverted tube is cleared, it indicates that the organism has the enzyme lactase to ferment lactose.

What does the absence of air bubbles in the inverted tube signify?

The absence of air bubbles in the inverted tube suggests that the organism does not produce CO2 during fermentation of the sugar being tested.

Can the Durham tube test be used with a variety of simple sugars?

Yes, the Durham tube can be used with different simple sugars to determine which ones an organism can ferment, as indicated by color change and gas production.

What is the significance of using the Durham tube in conjunction with a TSI tube?

Using the Durham tube with a TSI tube can provide additional supporting information about which sugars are fermented by an organism, as TSI contains multiple sugars.

What does a cleared inverted tube in a sucrose Durham tube indicate?

A cleared inverted tube in a sucrose Durham tube indicates that the organism has fermented sucrose, producing acid and CO2, and possesses the sucrase enzyme.

How can you interpret a red result in a Durham tube test for a simple sugar?

A red result in a Durham tube test for a simple sugar indicates a negative test, meaning the organism did not ferment the sugar and no acid production occurred.

Outlines

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🔬 Carbohydrate Fermentation Test with Durham Tubes

This paragraph describes the process of testing an organism's ability to ferment simple sugars using Durham tubes. The Durham tubes contain a broth medium with an inverted glass tube to collect air bubbles, indicating gas production. Phenol red is used as an indicator; it turns yellow when the pH drops due to acid production during fermentation. The presence of yellow color signifies the production of acid, suggesting the organism has the necessary enzymes to ferment the sugar. The absence of yellow color (remaining red or orange) indicates a negative result, meaning the organism lacks the specific enzyme to ferment that sugar. The inverted tube also helps to determine if CO2 is produced during fermentation. The paragraph also mentions the use of different sugars in separate tubes and the possibility of using these results in conjunction with TSI tubes for further analysis.

Keywords

💡Fermentation

Fermentation is a biological process where microorganisms like bacteria or yeast convert sugars into acids, gases, or alcohol. In the context of the video, it refers to the ability of an organism to break down simple sugars, which is a key indicator of its metabolic capabilities. The script discusses testing for fermentation using Durham tubes, where the presence of acid production turns the phenol red indicator yellow, indicating successful fermentation.

💡Durham Tube

A Durham tube is a type of test tube used in microbiology to detect gas production during fermentation. It features an inverted glass tube inside to catch air bubbles. The video script describes how the Durham tube is used to test for fermentation of sugars by observing changes in the inverted tube and the color of the phenol red indicator, which are indicative of gas and acid production, respectively.

💡Simple Sugars

Simple sugars, or monosaccharides, are the basic units of carbohydrates that can be easily metabolized by living organisms. The video script mentions testing for the fermentation of different simple sugars, such as lactose and sucrose, to determine which enzymes an organism possesses. The ability to ferment a particular sugar indicates the presence of specific enzymes, like lactase for lactose.

💡Phenol Red

Phenol red is a pH indicator used in the Durham tube to detect changes in acidity during fermentation. It starts as red and turns yellow when the pH drops due to acid production. In the video, the script explains that a yellow color in the Durham tube indicates that the organism has fermented the sugar and produced acid, as seen with the lactose tube turning yellow.

💡Acid Production

Acid production is a result of fermentation where sugars are broken down into acids. The video script uses the color change of phenol red as an indicator of acid production; a yellow color signifies that acid has been produced, while the absence of color change (remaining red) indicates no acid production, suggesting the organism lacks the enzyme to ferment the sugar.

💡Gas Production

Gas production during fermentation is often a byproduct of the metabolic process, particularly the production of carbon dioxide (CO2). The video script describes observing the inverted glass tube in the Durham tube to detect gas bubbles. If the tube is cleared by at least a third, it indicates that the organism can produce CO2 during fermentation, which is typically associated with acid production.

💡Lactose

Lactose is a disaccharide sugar found in milk and dairy products. In the video script, lactose is used as one of the sugars to test for fermentation in the Durham tube. The absence of a yellow color change in the phenol red indicator and no clearing of the inverted tube suggests that the organism does not have lactase, the enzyme required to ferment lactose.

💡Sucrose

Sucrose, commonly known as table sugar, is a disaccharide composed of glucose and fructose. The video script mentions sucrose as another sugar tested in the Durham tube. A positive result, indicated by a yellow color and clearing of the inverted tube, suggests that the organism has the sucrase enzyme necessary to ferment sucrose.

💡Enzymes

Enzymes are biological catalysts that speed up chemical reactions. In the context of the video, enzymes like lactase and sucrase are crucial for fermenting specific sugars. The script explains that the presence of acid and gas production in the Durham tube is evidence of the organism's ability to produce these enzymes, which are necessary for fermenting the respective sugars.

💡TSI Tube

TSI, or Triple Sugar Iron, is a type of agar medium used in microbiology to differentiate bacterial species based on their ability to ferment different sugars and their reactions to iron. The video script suggests using Durham tubes in conjunction with a TSI slant to provide additional information about which sugars are fermented, supporting the identification of the organism.

Highlights

Fermentation of simple sugars can be tested using Durham tubes.

Durham tubes contain an inverted glass tube to catch air bubbles.

Organisms with enzymes to ferment sugars can be identified through this method.

Phenol red is used as an indicator; it turns yellow if acid is produced during fermentation.

A yellow color in the Durham tube indicates acid production from fermentation.

A red or orange color suggests the organism lacks the enzyme to ferment the sugar.

The inverted glass tube can indicate gas production during fermentation.

Clearing of the inverted tube by at least a third indicates CO2 production.

Acid and gas production are consistent indicators of successful fermentation.

Sucrose fermentation results in a yellow color indicating a positive test.

No air bubbles in the inverted tube suggest no gas production during sucrose fermentation.

Different simple sugars can be tested in separate Durham tubes.

Durham tubes can be used alongside TSI tubes for additional information on sugar fermentation.

TSI tubes contain multiple sugars and can support Durham tube findings.

The process helps to determine which sugars are fermented by an organism.

Carbohydrate fermentation using Durham tubes is a valuable method in microbiology.

Transcripts

This video outlines

Fermentation of simple sugars testing this with the Durham, or what's often called the carbohydrate - this is a broth

medium so in the tube you'll notice that you have

an additional inverted tube inside which is a glass tube and that is there to catch air bubbles.

So we can test for the ability of an organism to ferment a particular simple sugar and we can have different sugars in different tubes

If the organism can ferment that particular sugar we say it has the enzymes with which to do so

We also can look to see if the organism produces gas in the course of

fermentation and that's what that inverted glass tube is for inside.

Now the indicator here is phenol red. Phenol red starts out red

which you actually see here on the left that looks almost like a uninoculated tube even though it's not. And

phenol red will turn yellow if the pH drops when an acid is produced.

So here on my lactose tubes on the left. I've got the yellow

which indicates acid is produced, the phenol red turned yellow

Any other color, orange, red

that we call that a negative that the organism does not have the particular enzyme in this case lactase to ferment lactose.

On the left here

We can see that this remained red so the phenol red did not react with an acid because there was not

Fermentation of lactose that produced an acid end product. Another thing to note here is that

inverted tube. So if that is cleared out at least a third of the way

Not just a little bit at the tip because sometimes that can happen during the manufacturing of the tube

But if there are enough air bubbles to clear out about a third of the tube

We say that the organism can also produce CO2 in the course of

fermentation. You would only see this with an acid production because that's going to be in line with the acid production and the fermentation.

On the right here, you've got the sucrose tubes the same idea again

If an acid is produced you get a yellow color. Now on this one you don't get the air bubbles produced at the top

Put that little bit closer to see

Yeah, you can see that

There's no air bubbles produced there

As opposed to one that does have the air bubbles you can see the clearing pretty well there I think.

So the yellow product acid production phenol red, which is our indicator turns yellow

So that in this case, since sucrose is a simple sugar

that's used

we can say that the organism is positive for the fermentation of sucrose or we can say has the

sucrase enzyme and

Right next to it here in the red

The red results that is a negative because again

We didn't get that acid production. And we can put a variety of

simple sugars in different tubes. One nice thing to do with these is to use them in conjunction with a TSI tube in particular.

A TSI slant, because TSI has multiple sugars in there. So this can help narrow down or give us additional

Supporting information as to which sugars are fermented and that is the carbohydrate

fermentation with Durham tube