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Portage Microbiology Lab Exam 5 Questions and Answers | Latest Version | 2025/2026 | Correct & Verified
What stain is commonly used to identify bacterial endospores under the microscope?✔✔ Malachite green
What is the purpose of the counterstain in a Gram stain?✔✔ To color Gram-negative cells
What is one sign of bacterial contamination in a broth culture?✔✔ Cloudy turbidity
What tool is used to transfer bacteria aseptically in lab experiments?✔✔ Inoculating loop
What is the name of the clear area around an antibiotic disc where bacteria do not grow?✔✔ Zone of inhibition
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What type of medium contains substances that allow some bacteria to grow but inhibit others?✔✔ Selective medium
What type of medium differentiates bacterial species by color change or colony appearance?✔✔ Differential medium
What is the primary use of MacConkey agar in microbiology labs?✔✔ To isolate Gram-negative enteric bacteria
What does a positive catalase test produce?✔✔ Bubbles
What reagent is added to test for the presence of catalase enzyme?✔✔ Hydrogen peroxide
What is the purpose of a Durham tube in carbohydrate fermentation tests?✔✔ To trap gas production
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