A sample taken from a sewage treatment plant is likely to have too many bacteria to count directly. What would be best done when determining the numbers of viable bacteria in the sample? Group of answer choices Filtration then spread plating the filtrate Serial dilution and spread plating the dilutions 16-streak plating of the wastewater sample All of the other answer choices are correct Optical density reading in a spectrophotometer
Question
A sample taken from a sewage treatment plant is likely to have too many bacteria to count directly. What would be best done when determining the numbers of viable bacteria in the sample?
Group of answer choices
Filtration then spread plating the filtrate
Serial dilution and spread plating the dilutions
16-streak plating of the wastewater sample
All of the other answer choices are correct
Optical density reading in a spectrophotometer
Solution
The best method for determining the number of viable bacteria in a sample that likely has too many bacteria to count directly would be "Serial dilution and spread plating the dilutions".
Here's why:
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Filtration then spread plating the filtrate: This method might not be effective because the number of bacteria might still be too high to count even after filtration.
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Serial dilution and spread plating the dilutions: This method is the most suitable because it reduces the concentration of bacteria to a countable level. By diluting the sample multiple times (serial dilution), you can get to a point where the bacteria can be spread on a plate and each individual bacterium can grow into a separate colony that can be counted.
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16-streak plating of the wastewater sample: This method is typically used for isolating a particular type of bacteria, not for counting the total number of bacteria in a sample.
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Optical density reading in a spectrophotometer: This method gives an estimate of the total number of bacteria, but it doesn't distinguish between live and dead bacteria. Therefore, it's not suitable for determining the number of viable (live) bacteria.
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All of the other answer choices are correct: This is not correct because, as explained above, not all the other methods are suitable for counting the number of viable bacteria in a sample with a high bacterial count.
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