Tuesday, September 17th 2013

Class date: Tuesday, September 17th 2013

Dear blog and blogreaders,

Today in microbiology we obtained our streak plate from the 30 degree incubator! (this streak plate had previously started in the 30 degree incubator, was transferred the the 25 degree incubator and was then placed back into the 30 degree incubator). Here is what our streak plate looked like before this last incubator trial:

   

When we obtained the sample from the 30 degree incubator this is what we found:

Growth/cream/non-pigmentation

Since there was growth but no pigmentation and if this bacteria was the same bacteria as the red pigmented bacteria it should have become red in the 30 degree incubator we concluded that this cream/non-pigmented bacteria and the red bacteria are two different types of bacteria. 

To further prove this statement, we created one last streak plate (a brand new one) from the pure soil sample. 

    

The pure soil sample.

Our new streak plate. 

We placed this streak plate in the 30 degree incubator to see what would occur one last time. 

Next, we obtained our agar slant test tube from the 25 degree incubator. This is what we observed. 

Looking very similar to our soil bacteria.....

Next, we prepared another agar slant test tube using a pure culture of this bacteria from the test tube labeled "S". The purpose of this was to obtain a purer sample. 

First we sterilized the loop.

Next we sampled the bacteria from the "S" test tube.

We then put the sample in the new agar slant test tube in a wave motion and labeled it "S2".

"S2"

Following that procedure, we prepared a gram stain of the "S" bacteria. 

First, we prepared a fixed smear of bacteria.

Max sterilizing the loop. 

Max putting distilled water into the sterilized loop. 

Max putting the water on the sterilized glass slide. 

Sterilizing the loop once again. 

Obtaining a pure sample of bacteria

Smearing the bacteria on the water droplet on the slide. 

Allowing the sample to air dry. 

Heat-fixing the sample. 

We covered the smear with crystal violet for  twenty seconds.

We then rinsed off the crystal violet with an indirect stream of DI water. 

Then we covered the smear with Gram's Iodine for one minute.

We rinsed the slide with indirect DI water. 

Next, we rinsed the slide at a 45 degree angle with 95% ethanol drop by drop until the color stopped running. 

Following that procedure, we rinsed the slide again with DI water,

Next we covered the smear with Gram's Safranin for one minute. 

Once again, we rinsed the slide with DI water.

Finally, we blotted the water from the slide with bibulous paper.

Our slide was now ready to be used under the microscope!

Max focusing the microscope.

The oil immersion lens in use and the oil.

We determined that this was gram-negative bacteria due to the very distinct rod shape. Once again,  Gram-negative bacteria is in the shape of rods and has a thinner cell wall than Gram-positive bacteria. Gram-negative bacteria has a Peptidoglycan layer sandwiched between two phospholipid bilayers and has a lipopolysaccharide on it's surface which is an endotoxin. Through this we are able to tell that this bacteria is not denatured by boiling, is antigenic, does not form a toxoid, has a low potency, has a low degree of specificity, has no enzymatic activity, and is pyrogenic (fever-causing).