Lab 9/29: Capsule Staining

Today, we determined whether our Unknown Bacteria C has a capsule around it or not. Capsules are highly organized firmly attached polysaccharide accessories to the cell wall which may contain lipids or proteins. If our bacteria is encapsulated, it is able to protect itself from being phagocytized or ingested. Therefore, encapsulated bacteria are able to survive longer in the body than non encapsulated bacteria.

The first picture shows the stains that we used: Nigrosin Stain, and Safranin
The Nigrosin was a black stain that we smeared across the slide with our bacteria on it. Its the stain that brings out the actual capsule. The Safranin stain stained our bacteria.

Encapsulated Bacteria (note: Not our unknown, just an example of what Encapsulated bacteria would look like)

The next picture reveals our bacteria to be non-encapsulated. Our bacteria has a dark inside and light outside where encapsulated bacteria would have a light inside and dark outside (making it look like white holes in a pink background). The picture directly above is encapsulated.

Lab 9/27: Gram Staining

We determined whether our Unknown Bacteria C was Gram Positive or Gram Negative. In order to do this we: 

1. Fixed a slide with a smear of bacteria

2. Stained the fixed slide with Crystal Violet Dye

3. Added Gram's iodine

4. 95% Ethanol was added as a de-colorizer solution which removed some of the stain

5. Added Safranin stain

Above are the fixed slides of our environmental bacteria (from the bathroom door) and our unknown bacteria.

The picture above is our unknown bacteria C

Above is the Gram stain of our Environmental Bacteria

Once the slide was stained, we looked at our bacteria using the oil immersion objective of the Compound Microscope, and determined that our bacteria is Gram Positive.

Lab 9/22: Bacteria Motility

In this class, we tested our unknown C bacteria’s motility. In order to test this, we used a .4% agar tube, and put a sample of our bacteria on a loop and stabbed it straight down into the agar. The .4% agar is solid enough that the bacteria will not spread around, but fluid enough that the bacteria is able to swim, if it is motile. If the bacteria is able to swim, the .4% agar tube will appear cloudy after the bacteria is grown. If it is non-motile, the bacteria will only grow in the stab line, and will not be cloudy.

Results: Unkown Sample C is Motile. Our environmental sample is nonmotile.

Lab 9/20: Determined Shape and Color of Bacteria

In lab, we

1.     Inoculated a  broth tube with unknown sample C

2.     Prepared a Streak plate for the unknown sample C to start colony morphology.

3.     Repeated a simple stain for our environmental and unknown sample C.

a.     There are 2 types of stains:

                                                        i.     Acidic, which binds to proteins that are positively chargedà Anionic

                                                       ii.     Basic, which binds to negatively charged nucleic acid and cellular components à Cationic

4.     We determined the shape of our unknown sample C and found that it was:

a.     Cream or tan colored

b.     Circular shape

c. Had Irregular edges