A Discovery & Simple Staining of the Pure Air Sample

A Discovery & Simple Staining of the Pure Air Sample

Class: Thursday, September 5, 2013

We excitedly opened the incubator to reveal the results our pure sample of the Steubenville air!

Pure culture of air sample

We zoomed in to get a closer look:

Magnified pure culture of air sample

In the original plate of the air sample, there were multiple kinds, colors, and shapes of microbes. We were curious as to whether this isolated bacteria expressed inhibitory behavior or not, whether it was antibiotic.  Dr. Pathakamuri let us explore this idea and explained to us how to figure this out.  On a new agar plate, we touched the inoculating loop to each of the original three bacteria from the first plate of the sample of air. We streaked distinct simple zig-zag lines per individual bacteria, taking care not to touch one streak of bacteria to the other.

Streak plate of three different bacteria 

Again, our purpose for doing this test was to see whether or not one of the bacteria exhibited inhibitory behavior. If it did, then the suspected inhibitory bacteria would take over the other two streaks of bacterial growth.

Next on the agenda was preparing a bacterial smear to stain our isolated bacteria. We stain bacteria so that we can see it more clearly under a microscope. This process is called a simple stain because it used to determine shape and size of bacteria.

First we wet our glass slide with distilled water. Then, after sterilizing the inoculating loop, we touched the loop to the pure air culture and then we transferred it to the glass slide, spreading the bacteria all around.

Adding a drop of water to the glass slide

Sterilizing the inoculating loop

Collecting a loopful of the pure bacteria

Spreading the pure bacteria on the glass slide

Next, we let the smear air dry.  After passing it through the bunsen flame three times, the smear was heat-fixed to the glass slide.

Heat-fixing the smear to the glass slide

It is time to stain the smear! The purpose for staining the bacteria is to then be able to identify it. 

We used a safranin stain, which takes around one minute to soak on the glass slide.

Safranin stain

Soaking our glass slide in safranin

We rinsed off our glass slide and lightly dried it will bibulous paper.

Rinsing the stain off our glass slide

Drying our slide with bibulous paper

Finally, we were ready to examine the stain of the pure bacteria from the Steubenville air!

This is what we found:

Magnified stained pure culture of air sample

 As we zoomed in, we found rod shaped bacteria, but also an exciting discovery - spores! The spores were oval in shape and linked, one next to the other.

Rod-shaped bacteria and spores

Dr. Pathakamuri showed us this poster to confirm our discovery.

The other interesting thing is the caption underneath this image of the poster. It says "Spores are central to each cell.  Shown is Bacillus subtilis, a common bacterium used in industrial processes."  Steubenville is an industrial area, so it was exciting to make this correlation.

The Dream Team: