Question

multiple choice question the streak plate technique works by using an inoculating loop to spread the bacterial sample in a pattern that thins it out but this only works if ______. there is a new diluted sample added at each step the inoculating loop is re-sterilized at each thinning step of the pattern the culture is pure to begin with the inoculating loop is sterilized only at the beginning of the plating process need help? review these concept resources. rate your confidence to submit your answer. high medium low © 2025 mcgraw hill. all rights reserved. privacy center terms of use

Explanation:

To determine the correct answer, we analyze the streak plate technique:

• The streak plate technique aims to obtain isolated bacterial colonies by thinning the sample. Re - sterilizing the inoculating loop at each thinning step (e.g., between different streak sections) removes most of the bacteria from the loop, so that when it is used to streak the next section, only a small number of bacteria are transferred, leading to further thinning.
• Option 1 is incorrect because we do not add a new diluted sample at each step; we use the same initial sample and thin it by streaking.
• Option 3 is incorrect because the streak plate technique can be used to isolate colonies from a mixed culture (it helps in purifying a culture, so the culture doesn't need to be pure initially).
• Option 4 is incorrect because if the loop is sterilized only at the beginning, there will be too many bacteria carried over in later streaks, and proper thinning (to get isolated colonies) will not occur.

Answer:

the inoculating loop is re - sterilized at each thinning step of the pattern