Preparing a Negative Stain of Sample S!

In lab we did a negative stain of sample S so that we could view the bacteria cells that are difficult to stain with basic dyes and are easily distorted by heat-fixation. Therefore, we created a dark background for the bacteria cells

To create this negative stain we first placed a tiny drop of Nigrosin stain near one end of a clean slide.





















Then we used a sterilized inoculating loop to transfer a small amount of bacteria, taken from our sample S, into the Nigrosin stain drop.

 

We then mixed the bacteria into Nigrosin stain drop.

We made sure to flame our loop before we set it down and we grabbed a second microscope slide and touched the Nigrosin stain drop at a 30-45 degree angle and quickly pushed the slide to spread out the drop.

Notice how the slide now has a thin film containing the Nigrosin stain and the bacteria from sample S.

We then waited for the slide to air dry completely and once it was done air drying we examined the stained smear under the microscope using the oil immersion lens.

Look at what we saw!!

(Fun note: It looks like stars in the night sky. The bacteria represent the stars and the purple background represents the night sky. It looks really cool!)