Medium in microbiology serve as mixed nutrients for the growth, reproduction, and metabolism of microorganisms. There is a wide variety of types, and the raw materials vary. However, regardless of the type of culture media, they must contain essential elements for microorganisms such as carbon source, nitrogen source, inorganic salts, growth factors, and water.
Additionally, a suitable pH, buffering capacity, redox potential, and osmotic pressure are also indispensable elements of culture media. To meet specific research needs, the preparation and sterilization of medium in microbiology are crucial. So, how do we prepare and sterilize medium in microbiology? Next, we will introduce the relevant steps in detail.
Based on the characteristics of the sample to be tested, precisely calculate the required volume of the culture medium and weigh it accurately according to the instructions. The electronic balance should be preheated for 30 minutes before use to ensure steady hand operation and attentive mind to avoid spillage of the culture medium. If spilled accidentally, stop weighing immediately, clean up the powder with a clean cloth, and re-tare the balance before weighing again.
For soluble starch, first, mix it into a paste with a small amount of cold water, then place it into boiling water; for hard-to-dissolve culture media, first add a small amount of purified water to shake and dissolve, then add water a second time to prepare it. If the culture medium needs to be subpackaged, ensure it is completely dissolved. For media containing agar, heat to melt before subpackaging into different containers for sterilization.
When making slant culture media, subpackage the media into test tubes; for making plate culture media or liquid and semi-solid culture media, subpackage into Erlenmeyer flasks. When subpackaging, use one hand to gently squeeze the spring clip to let the culture medium flow out, and the other hand to hold the test tube or flask sequentially. At the same time, keep the mouth of the tube or bottle clean to avoid contamination by miscellaneous bacteria.
After subpackaging, use silicone stoppers to tightly seal the tube or bottle mouth to filter the air and prevent contamination. Do not use absorbent cotton plugs to avoid unusability due to water absorption. The silicone stopper should closely fit the inner wall without gaps to ensure a good seal.
The sealed test tubes and Erlenmeyer flasks should be covered with kraft paper and tied tightly with a string, then labeled with the name of the medium in microbiology, group, and preparation date for subsequent sterilization needs. During sterilization, strictly follow the parameters specified in the culture media instructions. For slant and plate culture media, sterilize while the media has not completely solidified and is still hot.
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