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The introduction to each Group chapter refers to a table of differential characteristics, which will be your starting point. They were very useful for identifying unknown bacterial cultures, however. Bergey'S Online Manual Of DeterminativeIn lab, you will use the most recent edition of Bergeys Manual of Determinative Bacteriology, published in 1994 and reprinted in 2000, to help you identify your isolates. The organization of Bergeys Manual of Systematic Bacteriology makes it impractical for helping place unknown bacteria into major taxa, but it contains far more detail on the families, genera, and species and is far more up to date than the Determinative manual. You will need to consult this information in order to double check and finalize your identifications. We will require a 40 refundable deposit to cover loss of the volume if it is not returned. Please read the rest of this page after your team has obtained its copy. Chapter V of the Manual provides descriptions of all of the major Groups of bacteria, organized by phenotype. The following observations, listed in order of importance, will help you identify the Group to which your isolate most likely belongs. Remember, you must have a pure culture before conducting these observations. The Gram stain result (positive or negative) is the single most important step in differentiating major taxa. You must be certain of this result or your identification effort may be doomed from the start. See the document on preparing and interpreting Gram stains ( Gramstain.asp ) for more details. It is critical that you correctly identify your isolate as either an obligate aerobe (requires oxygen), a facultative anaerobe (can grow wo oxygen), or a microaerophil. Microaerophils, which grow only in the presence of low partial pressures of oxygen, are uncommon but will grow in our laboratory. We will not find obligate anaerobes, which cannot grow in the presence of oxygen. A bacterial rod has definite long and short axes, resembling a cylinder, often with rounded ends. We also have curved bacteria, and less commonly spiral or helical bacteria (having at least one full turn), branching cells, budding cells, club shaped cells, and cells with stalks. At 1000x we can estimate a dimension to the nearest 12, maybe 13 of a micrometer. Some motile species are notorious for not revealing motillity under the microscope. It is particularly useful for distinguishing groups of Gram negative organisms. We run the test on all of our isolates because it is very quick and inexpensive, although it may not be a useful differential characteristic for all of your isolates. Like the oxidase test, this one will be helpful in identifying some of your isolates, but probably not all. See the document on describing colony morphology ( describingcolonies.asp ) for details. From there, you should be able to conduct additional assays and observations that lead you to a specific genus and (hopefully) species.
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