1Thurs_Aseptic technique

1Thurs_Aseptic technique - Lab Exercise 3: Media,...

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Lab Exercise 3: Media, incubation, and aseptic technique OBJECTIVES 1. Compare the different types of media. 2. Describe the different formats of media, plate, tube etc. 3. Explain how to sterilize it, and how to distribute it in different formats. 4. Produce Nutrient agar (NA) plates, NA slants, and Nutrient broths (NB) which will be used in subsequent lab periods. 5. Know the laboratory equipment and culture media needed to develop and maintain pure cultures 6. Carry out aseptic technique for the removal and transfer of microorganisms for culturing. 7. Correctly sterilize and flame transfer instruments and tubes. 8. Properly incubate culture media at the appropriate temperature for the organism and the length of incubation. INTRODUCTION I. Media Media Containers: Media can come in liquid forms called broths. If a solidifying agent like agar is added the broth, is now a solid media. Solid media is prepared into Petri plates or in tubes as slants or deeps . If a larger tube is filled with a solid media it is called a Pour and is used to pour the media into a plate at a later time. Slants D e e p s P e t r i p l a t e
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Microbiology Media Preparation: Bacteria and fungi are grown on or in microbiological media of different types. The medium that is used to culture the microorganism depends on the microorganism that one is trying grow. Added certain substances to the medium can make it useful for selecting different types of organisms and differentiating between types as well. Sometimes a pH indicator may be added for differentiation of microbes based on their biochemical reactions: the indicators may turn one color when slightly acidic, another color when slightly basic. In this lab, your group will make media called nutrient broth and nutrient agar. These 2 media----one a liquid and the other a solid---are the exact same formula save for the addition of agar agar (really---agar agar), an extract from the cell walls of red algae. This particular medium will grow MOST bacteria that we use in lab. There are two general types of media. One is made with a chemical recipe. This medium is called a chemically defined media . Some of our media is made from extracts and digests of yeast, meats or other food sources. Since this type of medium has some unknown ingredients it is called complex media . It is really not very complex to make complex media: 1. rehydrate the powder form of the medium 2. stir and just bring to a boil the medium to get it all well dissolved 3. distribute the media into tubes or leave in flask for plates 4. autoclave to sterilize the tube media 5. autoclave the agar medium for plate production and then pour into sterile petri dishes and cool Sterilization and the autoclave When microbiological media has been made, it still has to be sterilized because of microbial contamination from air, glassware, hands, etc. There will be thousands of bacteria reproducing in the media so it has to be sterilized quickly before the microbes start using the nutrients up. The sterilization
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1Thurs_Aseptic technique - Lab Exercise 3: Media,...

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