Microbiology Lab Practice Exam PDF

**[Microbiology Lab practice exam ]** ### Practice Test #### Section 1: Serial Dilutions & Plate Count Lab 1\. Multiple Choice\ What is the primary goal of performing serial dilutions and plate counts?\ A. To measure bacterial motility\ B. To determine bacterial growth phases\ C. To measure viabl...

**[Microbiology Lab practice exam ]** ### Practice Test #### Section 1: Serial Dilutions & Plate Count Lab 1\. Multiple Choice\ What is the primary goal of performing serial dilutions and plate counts?\ A. To measure bacterial motility\ B. To determine bacterial growth phases\ C. To measure viable bacterial cell concentration\ D. To observe bacterial spore formation 2\. Fill in the Blank\ The principle that one bacterial cell can form one \_\_\_\_\_\_\_\_ on an agar plate. 3\. Short Answer\ Describe how you would create a 10⁻¹ and a 10⁻² dilution of a bacterial broth culture using pipettes and tubes of 9 mL of sterile saline. 4\. Calculation\ You transfer 1 mL from a 10⁻⁶ dilution into a tube containing 9 mL of sterile saline. What is the final dilution factor? 5\. Calculation\ A volume of 0.1 mL of a 10⁻³ dilution of bacterial culture was plated on nutrient agar and incubated at 37°C until 167 isolated colonies appeared. Calculate the concentration of living bacteria in the original culture. Express your answer in scientific notation with the correct units (viable cells/mL). #### Section 2: Genetic Diversity Lab 6\. Short Answer\ Explain what spontaneous mutations are, how they occur, and their potential consequences for a microbe. 7\. Multiple Choice\ Which of the following media types is used to assess genetic diversity in microbes?\ A. Neopeptone agar\ B. MacConkey agar\ C. Sabouraud dextrose agar\ D. YNB agar 8\. Short Answer\ Describe the difference between a wild-type strain and a mutant strain of bacteria. 9\. Fill in the Blank\ A mutant bacterial strain may lose its ability to synthesize a particular amino acid due to disruption in the \_\_\_\_\_\_\_\_\_\_\_ pathway. #### Section 3: UV Light Lab 10\. Multiple Choice\ Which of the following best describes how UV light damages bacterial DNA?\ A. It breaks the sugar-phosphate backbone\ B. It forms pyrimidine dimers\ C. It causes point mutations in DNA\ D. It inhibits DNA replication enzymes 11\. Short Answer\ What are pyrimidine dimers, and how do they affect DNA base pairing? 12\. Multiple Choice\ Why does UV light kill endospores at a lower rate than vegetative cells?\ A. Endospores have thicker cell walls\ B. Endospores have more DNA than vegetative cells\ C. Endospores are less metabolically active and have DNA repair mechanisms\ D. UV light does not penetrate the spore coat 13\. Fill in the Blank\ The procedure that spreads a bacterial culture across an agar plate using a sterile tool is called the \_\_\_\_\_\_\_\_\_\_\_ method. 14\. Short Answer\ Explain why UV light kills both vegetative cells and endospores, but endospores are more resistant to UV damage. #### Section 4: Antibiotic Resistance Lab 15\. Multiple Choice\ In the disc diffusion method for testing antibiotic susceptibility, what is measured to determine the effectiveness of the antibiotic?\ A. The color change in the medium\ B. The turbidity of the broth culture\ C. The diameter of the zone of inhibition\ D. The number of colonies formed on the plate 16\. Fill in the Blank\ A bacteria is considered \_\_\_\_\_\_\_\_\_\_\_\_ if it shows no zone of inhibition around an antibiotic disc. 17\. Short Answer\ Describe the steps you would take to perform the disc diffusion method to test bacterial susceptibility to antibiotics. 18\. Short Answer\ How would you interpret a large zone of inhibition around an antibiotic disc on a bacterial lawn? ### Answer Key 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.