LAB QUESTIONS – ASSESSMENT AND CRITICAL THINKING 1. When is a simple negative stain used? 2. Why do microorganisms remain unstained in the simple negative staining procedure? 3. What information can...

Extracted text: LAB QUESTIONS – ASSESSMENT AND CRITICAL THINKING 1. When is a simple negative stain used? 2. Why do microorganisms remain unstained in the simple negative staining procedure? 3. What information can be obtained from a simple positive staining procedure? 4. What is the difference between a simple and differential stain? 5. What is the reagent and purpose for each of the following gram stain steps? a. Primary stain b. Mordant c. Decolorizer d. Counterstain 6. Which step is the most crucial or most likely to cause poor results in the Gram stain? Why? 7. What part of the bacterial cell is most involved with Gram staining, and why? 8. What cell wall component is responsible for the acid-fast property of mycobacteria? 9. Is a gram stain an adequate substitute for an acid-fast stain? Why or why not? 10. Which area on a streak plate will contain the greatest amount of growth? The least amount of growth? Explain your answers. 11. What is a colony (as viewed on an agar plate)? How can a pure culture be obtained from a mixture of bacteria? 12. What is a selective agar? Why can it be of importance? 13. What is a differential agar? Why can it be of importance? 14. Describe how the following agars work: MacConkey, Blood, Phenylethyl alcohol, Mannitol salt. 15. What are the IMVIC series of tests? WHY / HOW are they used? 16. What is the catalase test? How is it used for colonies that are gram positive? 17. What is sputum and why is it important for microbiological testing? 18. What is the reason for testing staphylococci with a coagulase test? 19. What is the importance of group B Streptococcus agalactiae? 20. Starting with the MacConkey agar and IMVIC tests. Describe how a bacterium can be biochemically identified as Escherichia coli.