Question

A problem with ________ of cell number is that dead cells also scatter light. Select one:

a. viable counts
b. direct microscopic counts Incorrect
c. spread plate counts
d. optical density measurements
e. pour plate counts

Answer 1

Optical density measurements include dead cells in their readings because they scatter light, leading to potential inaccuracies when determining living cell counts.

Step-by-step explanation:

The problem with optical density measurements is that dead cells also scatter light, making it difficult to differentiate between live and dead cells without additional staining or procedures. Unlike methods like viable counts which may use specific dyes or growth conditions to enumerate only living cells, optical density measurements taken by a spectrophotometer assess turbidity caused by all cells present, living or dead. This can lead to inaccuracies when trying to ascertain the amount of viable cells in a culture.

Answer 2

The correct answer is d. optical density measurements.

Step-by-step explanation:

The optical density of a culture is measured to know the concentration of the bacteria in the culture. Spectrophotometer is the device used to measure the optical density of the cell.

The more the optical density more will be the concentration of bacteria and more will be the number of bacteria. Optical density is based on absorbance and scattering of light. So even dead cells can absorb and scatter the light.

So high optical density does not mean that there are more viable cells in the culture, therefore, it is a problem with optical density measurements of cell number is that dead cells also scatter light.