Question

Place this sample on a microscope slide, add water as necessary, cover with a coverslip, and observe on the microscope. Watch for motility, and if you have a phase contrast scope, look for sulfur granules inside the cells. If you are doing a Gram-stain, look for Gram-negative cells.

Short answer

Prepare slide with sample and water, cover with coverslip, observe for motility and sulfur granules, and do a Gram-stain to find Gram-negative cells.

Step-by-step solution

Prepare the Microscope Slide

Place the sample on a clean microscope slide.

Add Water

Carefully add a small drop of water to the sample on the slide.

Place the Coverslip

Gently place a coverslip over the sample to avoid air bubbles.

Observe Under Microscope

Observe the sample under the microscope. If available, use phase contrast to look for sulfur granules inside the cells.

Watch for Motility

Look for any movement within the sample to determine motility.

Conduct a Gram Stain (if applicable)

If doing a Gram-stain, stain the cells and observe for Gram-negative cells under the microscope.

Key concepts

Motility Observation

Motility observation is important for distinguishing between two major types of microorganisms: motile and non-motile.
Motility refers to the ability of organisms to move by themselves.
This is often achieved through structures like flagella or cilia.
To observe motility, place the sample on a microscope slide, add a drop of water, and cover it with a coverslip.
Make sure to avoid air bubbles when placing the coverslip.
Once your slide is ready, put it under the microscope and focus.
Look for any movement. Motile organisms will exhibit various types of movement such as swimming or tumbling.
Non-motile organisms, on the other hand, will remain stationary or show only Brownian motion (random movement caused by water molecules).
Observing motility helps in identifying and understanding the behavior of different microorganisms.

Phase Contrast Microscopy

Phase contrast microscopy is a technique that enhances the contrast of transparent and colorless specimens without using stains.
This is particularly useful for observing live cells and their internal structures.
When preparing a slide for phase contrast microscopy, use the same steps as mentioned before: place the sample, add water, cover with a coverslip, and observe.
Your microscope must be equipped with a phase contrast objective lens to use this method.
Adjust the phase contrast settings, and you'll notice more detailed images of the internal structures of cells.
One key feature to look for in sulfur bacteria, for example, is sulfur granules inside the cells. These granules will appear brighter compared to other cell components.
This method helps in identifying the presence of sulfur bacteria, which is essential for certain environmental and microbiological studies.

Gram-Stain Procedure

The Gram-stain procedure is a differential staining technique used to classify bacteria as either Gram-positive or Gram-negative.
Follow these steps for the Gram-stain:

• Prepare the sample and heat-fix it on a slide.
• Apply crystal violet stain and wait for a minute.
• Rinse with water and apply iodine solution for another minute.
• Rinse again and decolorize with alcohol or acetone for a few seconds.
• Rinse immediately and apply a counterstain (usually safranin) for one minute.
• Rinse and then observe under the microscope.

Gram-positive cells will appear purple because they retain the crystal violet-iodine complex.
Gram-negative cells will appear pink or red because they take up the counterstain.
This staining technique is invaluable for diagnosing bacterial infections and understanding bacterial cell wall structures.

Sulfur Granules Detection

Sulfur granules detection is crucial for identifying certain types of bacteria, particularly those involved in sulfur cycling, such as sulfur-oxidizing or sulfur-reducing bacteria.
To detect sulfur granules, you'll often use phase contrast microscopy because it enhances the contrast of these granules inside the cells.
Prepare your microscope slide with the sample and water, and cover it with a coverslip.
Adjust your microscope settings to phase contrast mode and start observing.
Sulfur granules will appear as bright, refractile bodies within the cells.
The presence of these granules can be a key indicator of the bacterial species' metabolic activities and ecological roles.
This type of observation is particularly useful in environmental microbiology for studying ecosystems like sulfur springs or marine environments.