The purpose of this lab was to observe microbes under the compound light microscope. By observing them we were able to distinguish their forms, if they were algae or protozoa; we were also able to identify the cell walls and the internal organelles. Ø First, we learned how to handle lab equipment and how to properly carry the Compound Light Microscope.
Ø By examining the pond water with the 40x lens, we were able to distinguish and identify the protozoa and the algae.
Ø Euglenoids are unicellular protozoa, which were recognized by its unique oval shape, and its flagella. We saw the nucleus, some spots that might have been a contractile vacuole used as a pump to remove excess water from the inside of the cell, as well as chloroplasts that enables it to supply some food through photosynthesis.
Ø We also identified Green algae and some rod-shape bacteria. For the bacteria we saw the cell wall, which gives support, it was moving which means that it had flagella, but due to the lack of resolution we were not able to see it.
Ø Green algae were colonial and it looked like seaweeds.
Ø By examining the hay infusion with the 40x lens, we were able to observe true motility and Brownian motility. Microbes were moving in a slower circular motion meaning they were showing true motility because particles in Brownian motion move in one direction in response to heat.
Ø By examining the yeast suspension with the 40x lens, we were able to observe unicellular budding yeast cell structures. We saw the cell wall of the eukaryotic fungus cells.
1. What is Brownian motion and why is it generally seen when bacteria are observed in liquid media?
Brownian motion is the random movement of particles suspended in liquid in response to heat. It is generally seen when bacteria are observed in liquid media because bacteria produce gas, making collisions with molecules in the liquid media.
2. How can Brownian motion be distinguished from motility?
Brownian motion is distinguished from motility because true motility requires a flagella or cilia to perform spiral movement, while Brownian motion it’s just the movement of particles when exposed to heat.
3. What are flagella? What is the difference between bacterial flagella and eukaryotic flagella?
Flagella are long appendages of a cell composed of microtubules used for motility. Eukaryote flagella are composed of nine pairs of microtubules and they move the cell by sliding the adjacent pairs causing the flagella to bend. Bacterial flagella are long and thing appendages composed of the protein flagellin and a single microtubule.
4. In wet mount preparations, is it possible to see eukaryotic flagella? Bacterial flagella? Why or why not?
In wet mount preparations it is possible to see eukaryotic flagella because they are large and have many microtubules. Bacterial flagella can’t be seen in wet mount preparations because it has only one microtubule and it’s so thin that it can’t be seen with the resolution of the compound light microscope.
5. What advantage does a hanging drop preparation have over a standard wet mount for the observation of motility?
The advantage that a hanging drop preparation have over a standard wet mount for the observation of motility is that the hanging drop offers a better view of true motility and it doesn’t dry out quickly.