Appendix B SCI250 Ver.docx

Appendix B SCI250 Ver.docx

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  Appendix B SCI/250 Version3 1 B University of Phoenix Material Appendix B – Identifying Bacteria Bacteria identification is accomplished in a number of ways. Two common tools microbiologists use to identify unknown bacteria include dichotomous key and biochemical tests. The dichotomous key is useful when a microbiologist only needs to know which group an unknown microbe belongs to on a general level. When a microbiologist needs to identify a specific bacterium, biochemical tests are used. PART ONE: GENERAL BACTERIA IDENTIFICATION Review the dichotomous key in Figure A, the bacterial shapes in Figure B, and the Gram stain information below. You will use all three to determine to which major group unknown bacteria belong. Figure B: The most common bacterial shapes. [Figure 4.1 in Microbiology text] Shape Types: Comma, or Club-shaped, rods = Vibrio Rods = Coccobacillus, Bacillus Spherical = Coccus Spiral or Helical = Spirillium, Spirochete
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  Gram Stain Results: Purple= Gram positive Red = Gram negative Neither purple nor red = No cell wall (neither Gram positive nor Gram negative) Review Figure C on the following page. Use Figure C to identify the type of arrangement displayed by the unknown bacteria. Read through the Sample Identification on the following page for an example of how to identify bacterial groups and arrangements using Figures A, B, C, and the Gram stain results. Figure C: Arrangement of Bacteria Rods and Clubs Single Strepto- Cording Snapping Palisades Chinese Letters Cocci Single Diplo-
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  Tetrad Sarcinae Staphylo- Strepto- Sample Identification After performinga Gram stain, you observe the following under a microscope: (Cells are stained red.) · Begin with item 1 on the dichotomous key (Figure A). Because the organisms are red, they are not Gram-positive. According to the key, continue to item 3. · Because the organism is red (not clear or another color), it is indeed Gram-negative according to item 3. The key directs you to item 5. · Consider the shape of individual cells for item 5. According to Figure B, the shape type is closest to spherical. (Note: spherical is circular.) · The bacteria belong to the Gram-negative cocci group. · Now use Figure C to describe arrangement of bacteria. (The bacteria are not rod- or club-shaped, so focus on the cocci arrangements.) Identify the arrangement that is most prominent.
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  · The bacteriaare arranged in a diplo- fashion. · Enter the group and arrangement in the table. Application Use Figures A, B, C, and Gram stain results to identify group and arrangement of bacteria. Continue to Part Two after completing the table. View from Microscope Group of Bacteria Arrangement (stained red) Gram-negative cocci Diplo- (stained purple) (stained purple) (stained red) (stained red) (stained purple)
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  (stained purple) PART TWO:CAse study scenario: identify specific bacteria through biochemical testing To gain an understanding of the processes involved with identifying bacteria through biochemical tests, access Chapter 6 of the text in WileyPlus located on the Week One course page. Once in WileyPlus (Chapter 6), select the “Bacterial Identification by API” link located under the heading, Take Another Look. Once selected, review the information and watch the Flash-animated movie (animation) located within this link. Then, review the following scenario and answer the questions that follow. Case Study A recent outbreak of food poisoning has occurred in a community. One possible source of contamination may be the produce that is grown and distributed locally at a farmer’s market. A test sample of some of the produce revealed evidence of bacterial contamination. The bacteria sample was tested in a microbiology lab and showed the results that follow. The laboratory also performed a Gram stain of the isolated bacteria and ran a number of biochemical tests to aid identification. The biochemical tests were assayed using the Analytical Profile Index (API) 20E system for identification of Enterobacteriaceae and other gram-negative bacteria. Figure 1. Microbiology laboratory results – Unknown bacteria present on produce (API Results) Figure 2. API Results of Unknown Bacteria in Text Format Gram stain: Gram-negative ONPG ADH
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  LDC ODC CIT H2S URE TDA IND VP GEL GLU Bacteria: Unknown + - + + - - - - + - - + MAN INO SOR RHA SAC MEL AMY ARA + - + + -
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  + - + Based on Gramstain results and the knowledge that this bacterium caused food poisoning, the laboratory is able to narrow down the possibilities to three bacterial strains. Figure 3 shows the API results: Figure 3. API Results of Known Bacterial Strains in Text Format Gram stain: Gram-negative ONPG ADH LDC ODC CIT H2S URE TDA IND VP GEL GLU Bacteria: Salmonella - - + - - - - - - - -
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  + MAN INO SOR RHA SAC MEL AMY ARA + - + - - + - - Gram stain: Gram-negative ONPG ADH LDC ODC CIT H2S URE TDA IND VP GEL GLU Bacteria: Shigella - - - -
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  - - - - - - - + MAN INO SOR RHA SAC MEL AMY ARA - - - - - - - - Gram stain: Gram-negative ONPG ADH LDC ODC CIT H2S URE TDA IND VP
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  GEL GLU Bacteria: E. coli + - + + - - - - + - - + MAN INO SOR RHA SAC MEL AMY ARA + - + + - + - + Application Comparethe API biochemical test results in Figure 2 (unknown bacteria from produce) with API test results in Figure 3 (known bacterial strains identified in the gray boxes on the left). The bacterial strain in Figure 3 that matches Figure 2 will identify
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  the bacterial straincausing illness. Based upon your observations, which of the bacteria in Figure 3 is the most likely cause of the food poisoning outbreak? ©2008 University of Phoenix. All rights reserved. Appendix A SCI/250 Version 3 1 University of Phoenix Material Appendix A – Cell Division in Bacteria After reading Ch. 6 in Microbiology: Principles and Explorations, fill in the following matrix. List the four phases of bacterial growth and briefly describe what happens in each phase. List and describe at least four methods used to measure bacterial growth. List at least two physical factors that influence bacterial cell growth. Briefly describe how bacterial growth responds to changes in those factors. List at least two nutritional factors that influence bacterial cell growth. Briefly describe how bacterial growth responds to changes in those factors. List and describe at least two events that occur during the process of endospore formation (sporulation). Note: Visit Chapter 6 of Microbiology: Principles and Explorations in WileyPlusto view the Endospore Formation Animation found under the Animated Concepts Section.
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  What is thefunction of a bacterial endospore? Explain in your own words. ©2008 University of Phoenix. All rights reserved.