Question

A scientist is examining motile protozoa. He wishes to determine their direction of movement without the use of chemical dyes or transfection of the cells. Which of the following microscopic techniques is least likely to be useful?

1) Bright-field microscopy
2) Phase-contrast microscopy
3) Fluorescence microscopy
4) Confocal microscopy

Answer 1

Bright-field microscopy is the least likely technique to determine the direction of movement of motile protozoa without using chemical dyes or transfection of cells.

Step-by-step explanation:

The least likely technique to determine the direction of movement of motile protozoa without using chemical dyes or transfection of cells would be 1) Bright-field microscopy. Bright-field microscopy lacks contrast in live specimens due to the diffuse resolution caused by differences in refractive index between components of the specimen.

On the other hand, 2) Phase-contrast microscopy enhances contrast between parts of a specimen with higher refractive indices and lower refractive indices, making it well suited for examining live, unfixed, and unstained specimens. 3) Fluorescence microscopy is particularly useful in clinical microbiology, allowing the identification of pathogens or specific molecules and structures within cells using fluorochromes.

Therefore, the least useful technique among the given options is Bright-field microscopy.