Thursday, October 17th, 2013

*This blog does not reflect Franciscan University in any way*

Dear Blog and Blog Readers, 

Today we checked the tests we had inoculated last class: indole, urea, nitrate, methyl-red, citrate. 

Citrate Test

Since the color of the agar slant was Persian Blue this test is positive and the bacteria does utilize 

citrate. 

Urea Test

The tube on the right is an uninoculated tube and the tube on the left is the tube inoculated with S. This test turned out to be partially negative because the color of the inoculated turned slightly but not completely pink. 

Methyl-Red Test

The first step was to pour half of the MV-VP test tube into another test tube so we could do an oxidase test with it. 

Max pouring the broth.

Next in one of the test tubes we dropped 6 drops of methyl red .

Sam dropping Methyl Red into the MV- VP test tube.

Immediately our reaction was as follows:

Right test tube: MV-VP with Methyl-Red

Left test tube: MV-VP without Methyl-Red

This indicated a slightly positive test  and therefore is it evident that S can ferment glucose via mixed-acid fermentation. 

Voges-Proskaur Test

In the other MV-VP test tube we dropped 15 drops of reagent A (alpha-naphthol) and 5 drops of reagent B (KOH).

Max dropping reagent A and B.  We shook the test tube and then let it sit for 30 minutes.

This indicates a positive test because of the red color; therefore, the bacteria does ferment glucose via butanediol.

Nitrate Reduction Test

We dropped 5 drops each of reagent A and B (sulfanic acid and dimelthy-alpha-napthylamine, respectively) in the nitrate broth tube and this was our result. 

This indicates a strongly positive test; therefore, S can reduce nitrate to nitrate ions or nitrogen gas.

Oxidase Test

We took our agar slant test tube labelled T and swabbed some of the growth.

We then dropped a few drops of oxidase reagent on the test tube. The swab turned purple immediately which is indicative of a positive test. 

To make sure we dumped the rest of the reagent in the test tube labelled T.

The bacteria growing there quickly turned purple, confirming our positive result.

Indole Test

Max dropping 5 drops of Kovac's reagent into the Tryptophan broth. 

This test was negative due to a yellow layer on top instead of red. This indicated that the bacteria S does not split tryptophan into indole and pyruvic acid.

Lastly, we observed Rhizopus fungus growing on a sandwich under the microscope.

We also made another streak plate of our bacteria "S" to use next class.