Potato dextrose agar is widely used in microbiology and mycology. This guide tells you everything that you need to know about the medium, allowing you to have all the information in one convenient place. This includes its uses and characteristics.
What Is Potato Dextrose Agar?
Potato dextrose agar, known by the acronym PDA, is used to grow and maintain fungi. It is a general purpose medium. This means that it can be used to grow a wide range of bacteria, including yeasts and molds.
This medium is made from potato infusion, hence the name. This infusion is extracted from the potato. Dextrose, a type of simple sugar, is also added to the potato infusion.
Potato dextrose agar can be accompanied by acid to slow down the growth of the bacteria.
What Are The Uses Of PDA?
This is quite a versatile medium, as it has multiple uses. For instance, potato dextrose agar can be used to:
- The medium can be used to determine the presence of yeast or mold in food, primarily dairy products.
- It can be utilized to find out how much yeast or mold is present in a cosmetic product. This is best done when combined with chlortetracycline.
- It has the ability to cultivate specimens of yeast and mold.
How Is PDA Made?
It is super simple to form your own PDA. All you need to do is follow these simple steps.
- Wash a large quantity of chopped but unpeeled potatoes (approximately 200 grams/ 7 ounces).
- Begin boiling these potatoes in 1 liter of distilled water. Leave them to boil for roughly 30 minutes, during which the potatoes will become soft.
- Filter the broth via a cheesecloth.
- Add more distilled water to the drained mixture. You should also add 20 grams of both agar powder and dextrose. These are essential ingredients, which is why they are included in the medium’s name.
- Use an autoclave to sterilize the mixture.
To complete the above instructions, you will need the following pieces of equipment:
- 200g of potatoes: as suggested by the name, this general purpose medium is made from potatoes. These can easily be purchased from your local supermarket.
- 1 liter of distilled water plus more for later
- A pot: You will need a fairly large pot to bring these potatoes to the water, given that it needs to be capable of containing an entire liter of water.
- A hob: An ordinary cooking hob will suffice to form this mixture.
- A Cheesecloth: primarily used in cheesemaking, this utensil will be used to separate the broth from the rest of the pot’s contents.
- 20g of agar powder: this plant-based powder is used to thicken mixtures in baking and cooking. Consequently, it will thicken this mixture too. Some supermarkets sell agar powder. If you can’t get your hands on it, you can order agar powder online.
- 20g dextrose: this is a simple sugar usually made from wheat, though it can also be constructed from corn.
- An autoclave: this is a complex scientific contraption, usually found in a lab. Unlike the other objects on this list, most of which are found in the household or can be bought from a supermarket, an autoclave is harder to acquire. This device can ensure that the potato dextrose agar reaches the necessary temperature and sterilizes it.
If you need to make a larger portion of PDA, feel free to adjust the measurements. As long as you keep them in the same ratios, the mixture should still work.
What Are The Characteristics Of PDA?
In terms of pH, the potato dextrose agar should be 5.6, with a leeway of 0.2pH on either end of the spectrum. So if your mixture has a pH of 5.4 or 5.8, you should not be concerned.
However, if it is outside of this range, something could be wrong with the PDA. You can use pH testing strips to determine its level, though they do not give the most accurate results.
The PDA will look different depending on how you are using it. Different results will cause the PDA to react differently.
What Are The Limitations Of PDA?
As a general-purpose medium, potato dextrose agar can be used for a wide array of bacteria. However, the downside of this is that it can only give you a general overview.
If you want a more specific analysis, you might want to try a differential medium. They enable you to determine key differences between microorganisms.
Moreover, you may want to examine the results under a microscope if you wish to get more detailed information.
How Should PDA Be Stored?
Potato dextrose agar should not be put directly in sunlight. Instead, you might want to keep it in a cool and dry place. Ideally, it should be kept in the range of 2°C and 8°C. If improperly stored, PDA may not be effective.
Once produced, it can be kept for roughly 12 weeks. After this time, we do not recommend using this bacth of PDA. You should use an airtight container to store this mixture.
Safety Warnings When Using PDA
As with any laboratory experiment, you must obey certain safety rules when using PDA. Namely, these are:
- Do not consume PDA. It is not designed for human consumption. Plus, it is unlikely to taste very pleasant!
- When making the mixture, avoid touching it or getting it in your eyes. If you get it on you, wash the area with water immediately. The mixture is unlikely to be too harmful to the skin, but it can cause some irritation, particularly if you have sensitive skin. If your skin becomes irritated afterward, it is recommended that you consult a doctor. As a safety measure, you can wear safety goggles and a pair of gloves to protect your eyes and hands respectively.
- PDA is best kept in the lab. Used in scientific experiments, we do not recommend using it elsewhere.
- The mixture should be made in a sterile laboratory environment. Clean the production area before and after use.
- When heating the potatoes, be careful not to burn yourself. If you acquire a burn, run the infected area under cold water, preferably for 20 minutes. Cover the burn with cling film to stop it from becoming infected. If the burn is substantial, go to the emergency room straight away.
Frequently Asked Questions
Which Media Is Best For Fungal Growth?
Aside from PDA, there are a few different general mediums that are excellent when it comes to fungal growth. You may want to opt for Sabouraud dextrose agar (SDA).
Named after its creator, Raymond Sabouraud, this mixture contains peptones. It has the same pH as PDA. Plus, it also contains both dextrose and agar, making this medium very comparable to PDA.
You can also use a malt extract agar, which is made up of maltose, Dextrin, peptone, and glycerol. Furthermore, you can also utilize a brain heart infusion (BHI), another well-known growth medium.
As the name suggests, this mixture is made from brain and heart infusions, namely from pigs or bovines. Thus, this might be problematic to vegan and vegetarian mycologists.
What Are Fungicides?
Fungicides are chemical mixtures that are made to kill fungi. They do this by stopping the fungi from developing. You might want to use a fungicide if one of your plants has become infected with fungi.
Fungicides can be really useful since some fungi can be really dangerous, particularly in agriculture.
PDA is a fascinating medium, particularly if you are interested in the world of mycology. After reading this informative guide, you will know everything about potato dextrose agar, including its uses and formation.
So, if you wish to perform your own experiments with mold and yeast, you are now in a good position to do so!
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