01_AsepticTechnique_091009 - ASEPTIC TECHNIQUE and...

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ASEPTIC TECHNIQUE and MICROSCOPY LABORATORY EXERCISE #1 Rev: 3/10/10 ASEPTIC TECHNIQUE Bacteria exist in their natural habitats as mixed populations containing many different species*. The study of the individual members of a microbial community is dependent on being able to isolate the various microbes. Solid media are essential for the isolation and separation of bacteria that may be in a specimen. When a mixture of bacteria is spread across the surface of a solid medium, individual organisms will be separated from one another and will multiply at the sites where they were deposited. A COLONY is the resulting MACROSCOPIC GROWTH , i.e. visible aggregate, which usually consists of the progeny of a single microbe. One clone of a single species can therefore be separated from the mixture of species and then transferred to another medium (“ SUBCULTURED ”) where it will grow and can be maintained as a PURE CULTURE . The macroscopic appearance of colonial growth can be very distinctive for individual species. Observation of the gross features of colonies, i.e. COLONIAL MORPHOLOGY , is very important. The color, consistency, surface texture, shape, and size should all be observed; these features can provide clues as to the identity of the microbe. The cells of a colony can also be described MICROSCOPICALLY ; differential staining techniques also aid in categorization of bacteria based on cell size, shape, arrangement, and staining. To work with cultures, it is important that they be handled ASEPTICALLY (i.e. in a sterile manner). They must not be permitted to contaminate you, your fellow workers, or the environment. Similarly, the cultures must not be contaminated with “extraneous” organisms, from you or from the lab environment (i.e. air-borne bacteria and fungal spores). * In addition to other micro-/macro-organisms, e.g. algae, fungi, protozoa, college students, etc. … 1
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Preparations After this lab, review your lecture notes or text regarding the physics of how and why a microscope functions; particularly review why you are using oil immersion and why Gram staining differentiates bacterial types from one another . ( Parts of a Microscope - See both Appendix B of this lab and chapter 2 of your text; both discuss the anatomy of a “compound, bright-field microscope." Preparations – For every lab, you must have an organized workspace . Work that can be accomplished quickly and efficiently will minimize the time of exposure of sterile media
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