Negative Stain of Mystery Bacteria & Steubenville Air Sample

Negative Stain of Mystery Bacteria & Steubenville Air Sample

Class: Thursday, September 19, 2013

Today, after checking out the growth our mystery bacteria, we decided to do a negative stain of it.  A negative stain is when you create a dark background around the transparent cells.  The purpose of this type of stain is to see the outline of the bacteria more clearly.

Nigrosin on glass slide

We started by adding a drop of a dark stain called nigrosin on one end of a glass slide.

Next, after sterilizing the innoculating loop, we transfered a small amount of our mystery bacteria from the test tube and mixed in with the drop of nigrosin stain on the glass slide.

Capturing small loop of mystery bacteria

Mixing mystery bacteria into stain

After again sterilizing the innoculating loop, we spread the stain across the glass slide using another clean glass slide, leaving a feathered edge on one end.

Sliding stain across

Sliding stain across

Feathered edge of stain of mystery bacteria

Magnified view of mystery bacteria

We allowed the stain to air dry, and afterwards we examined the mystery bacteria under a microscope.

Next, we did another negative stain, using the same technique, but this time of the Steubenville air sample:

Capturing small loop of air sample

Sliding stain across

After letting the stain air dry, this is what we viewed under the microscope:

Magnified view of air sample

 Lastly, here is an update on what grew on the agar plate and in the broth from Juliet's tea.  The original growths of the tea were swapped: what grew on the agar plate was swabbed and placed in the broth, and what grew in the broth was swabbed and placed on the agar plate.

Tea bacterial growth