1. Amanda Kain, Kelsey, Justin 01-14-14
Lab 4 Report
Smears and Simple Stains of Microbes
Introduction:
In this lab we stained four different micro organisms to view them under the microscope and
observe the different characteristics. We had to use stains because the bacteria and yeast cells
are almost transparent without them.
Experimental Procedure:
We obtained microbes from a solid culture and made a smear on glass slides which we then
stained using various agents, allowing the slides to air dry before and after staining. The
microbes we used included; Escherichia coli, Bacillus megaterium, Staphylococcus epidermidis,
and Candida sp. For the Candida sp. we used the methylene blue stain, for B. megaterium we
used the safranin stain and for the S. epidermidis and E. coli we used the crystal violet stain.
When the stained microbes were ready we viewed them at 1000X magnification under oil
immersion. Refer to Microbiology Manual Lab 4 for step by step procedures.
Results:
When viewed under the microscope at a final magnification of 1000X the Candida sp. (yeast
cells) appeared as round single cells in small clusters, we observed budding of a yeast cell as
well. The B. megaterium appeared as rod-shaped single cells, arranged in clusters that seemed
2. to form as if they were surrounding bubbles. The S. epidermidis (1000X) appeared as round-
shaped, single cells which gathered in many small clusters. The E. coli (1000X) appeared as
rod-shaped, single cells that formed big, long strand like clusters.
Sketches attached.
Discussion:
Each microbe had its own unique characteristics. However, the three microbes that were of
the bacteria domain; E. coli, B. megaterium and S. epidermidis, seemed to be much smaller in
size compared to the yeast cells of Candida sp. The B. megaterium had a very recognizable
"bubble" like formation, the E. coli forming long stranded clusters and the S. epidermidis formed
several small clusters. The Candida sp. slide differed in size, containing larger cells, and did not
have as many clusters as any of the other slides.
Conclusion:
We were able to clearly view all of our microbes using stains, which are attracted to the
bacteria and yeast cell's slight negative charge. Stains are used in microbiology to be able to
view, observe and identify microorganisms. Bacteria and other micro organisms would be very
hard to observe without stains because they are otherwise transparent. It was interesting to see
the organisms and their unique arrangements and sizes in comparison to each other. The yeast
cells, for example, we're larger than the other organisms and it being the only non-bacterial
organism we viewed raised some curiosity, like possibly being an eukaryotic cell, containing
more/different cellular makeup, such as organelles, etc...could be responsible for the size and
