Which step in the streak plate procedure involves sterilizing the inoculating loop before streaking a new section of the agar plate?

• A. Incubating the plate after streaking
• B. Flaming the loop between streaks
• C. Labeling the bottom of the agar plate
• D. Adding bacterial sample to the first quadrant

Answer: (B)

Verified step by step guidance

1. Understand the purpose of the streak plate method: it is used to isolate individual bacterial colonies by diluting the sample across different sections of the agar plate.
2. Recognize that sterilizing the inoculating loop between streaks is essential to prevent carrying too many bacteria from one section to the next, which helps achieve isolated colonies.
3. Identify the step where the inoculating loop is heated (flamed) until red-hot to kill any remaining bacteria before streaking a new section of the plate.
4. Note that flaming the loop between streaks is the critical sterilization step that ensures the dilution of bacteria across the plate.
5. Confirm that other steps like incubating the plate, labeling the plate, or adding the bacterial sample occur at different points and do not involve sterilizing the loop.