1. What structures are visible in the unstained Tetrahymena sp.? With iodine? With

methyl green?

In an unstained Tetrahymena sp. fast- dot like organisms are observed

under the scanner. These are transparent structures with colorless outlines and

may be used for identification of some of the organelles such as vacuoles and cell

membrane.

With the cell stained with iodine, the nuclei and the glycogen vacuoles are

now visible as the stain enters the cell and locomotory organelles such as cilia can

also be seen.

With the cell stained with methyl green, macronuclei and micronuclei can

be observed as well as its nuclei.

Figure 1. Unstained Tetrahymena sp. under the scanner

Figure 2. Vacuoles and cell membrane of unstained Tetrahymena sp. under LPO

Figure 3.Tetrahymena sp. stained with Lugol’s Iodine (IKI)

Figure 4.Tetrahymena sp. stained with Methyl green

Figure 5.Tetrahymena sp. stained with Methyl green observed under HPO

2. Do all stains enter the cell or just render more contrast to the background?

All stains entered the cell. With the cell stained with iodine, it rendered a

contrast to the background because it gave off a darker color. With the cell stained

with methyl green, it blended in with the background displaying the cell’s outline

and the visible structures.

3. By providing a dark background, would the cell structures look clearer?

Dark background enhances the contrast of the image to bring out fine

details. Reduction in intensity of the light that had not passed through the

specimen would create a grey background and increase contrast even more, with

some parts of the specimen darker and other parts of the specimen brighter than

the background.

4. Tabulate the different structures seen under each of the stains used. Explain the mechanism for each reaction.

OBSERVATION MECHANISM/REACTION

Tetrahymena sp. stained with Lugol’s Iodine

Locomotory organelles such as cilia are already visible and ass the stain enters the cell, the nuclei and the glycogen vacuoles are now visible.

Iodine is used in chemistry as an indicator for starch. When starch is mixed with iodine in solution, an intensely dark blue color develops, representing a starch/iodine complex. Starch is a substance common to most plant cells and so a weak iodine solution will stain This polysaccharide is produced by all green plants as an energy store. One chain contains hundred to thousand glucose units, which form a helical structure in which iodine can be trapped which results in the blue color of starch upon iodine staining.

Tetrahymena sp. Stained with Methyl green

Macronuclei and micronuclei of the cell can be observed and the nuclei can also be seen.

Methyl green has seven methyl groups rather than crystal violet's six. This seventh group is easily lost and the dye reverts to crystal violet. For that reason there is invariably a quantity of crystal violet mixed with the methyl green. It is also a basic dye used as a chromatin stain, as a differential stain for RNA and DNA, and as a tracking dye for DNA in electrophoresis. It stains cell nuclei light green. This superior formulation of methyl green is suitable for use with a wide range of enzyme substrates.