Day 8: 5/23

A day of second conclusions:

Follow up on Urea and Litmus:

The urea test we examined still appeared a peachy yellow in color meaning our bacteria does not actively use urease to degrade urea into carbon dioxide and ammonia. (if it did the raise in pH from ammonia production would have turned the solution a bright pink)

The Litmus milk finally showed our bacteria to be more active in this test. With the addition of further curdling, this test proves more positively that our bacteria can ferment lactose. The curds appeared white, meaning that they were actually acidic.

Follow-up on Differential Plates:

MacConkey plate had some growth meaning our unknown bacteria is actually a Gram negative (WHA wha wha) Even though we thought that it was gram-positive. The bacteria that grew on the plate was slightly pink meaning our bacteria does ferment lactose.

Next the Mannitol plate had no growth because our bacteria is not salt tolerant and is not a halophile (a bacteria that can tolerate 7.5% NaCl and grow)

Onward to the EMB plate or Eosin Methylene Blue Agar used to differentiate the type of enteric bacilli.  Our bacteria was positive for the test and had some growth.  It is a weak lactose fermentor and according to the diagram our bacteria is an Enterobacter aerogenes. Because it was a lower acid producer during fermentation of the sugar yielded a pick colony because less dye is precipitated.

Then we checked the PE agar plate and we had no growth because this test was to isolate gram-positive bacteria and the medium slows the the growth of gram-negative and allows gram positive growth.

Finally the Blood agar plate test showed our bacteria to be alpha hemolysis meaning it only partially lyses red blood cells.  There were small dark patches on our medium plate to signify this. One of the group plates had the other two types of hemolysis beta (bacteria secretes enzymes that completely breakdown RBCs) and gamma (nonhemolytic bacteria that does not damage RBCs

We again had a second conclusion and reexamined the strephtlyococcus test for Theresa and found out that she was indeed a positive and quite possibly a carrier (oh no! stay away!)

To close out the day we watched Contagion! (moral of the story: don’t shake your chef’s hand)