Test results for fermentation of our bacteria

Test Results for Fermentation of Our Bacteria

Class: Thursday, October 24th, 2013

Last week we prepared a bunch of tests (seven) and today all we did was observe those tests and determine what they meant (positive or negative for fermenting the media on the agar plate). If the bacteria fermented and grew, the result proved positive. And today our bacteria did not prove itself totally boring, IT WAS POSITIVE FOR SALT TOLERATION! IT LOVES SALT! I guess you could say its a HALOPHILE! Sorry, as you can see, we were pretty excited about having a positive test for once.. This rarely happens.

FIRST TEST: THIOGLYCOLLATE

With this we were testing our bacteria on whether it would grow in the presence of air, no air, or both. If it was able to grow in the presence of air, this would be a positive test for classifying the bacteria as obligate aerobe. If it grew and multiplied without the presence of air, this would classify the bacteria as obligate anaerobe. And lastly, if the bacteria can grow with and without the presence of oxygen it is classified as facultative aerobe.

Our Facultative aerobic bacteria

SECOND TEST: DNase DNA HYDROLYSIS TEST
Before we could determine the ability of our bacteria to hydrolyze DNA, there was a step that we had to take. We poured 1N HCL into the plate, flooding it. This allowed us to examine the plate for a clear area around our bacteria. If there were a clear area around the bacteria, this would be a positive test for our bacteria to posses a digestive  enzyme (DNase).

Negative for DNase :(

HCL used to flood the plate

What a positive test would look like

THIRD TEST: EMB: EOSIN METHYLENE BLUE
In my opinion, this test was a little pointless for our bacteria. This is because our bacteria is gram -  positive, which we already established in one of our earlier labs. This test was performed to distinguish between those bacteria that ferment lactose and /or sucrose and those that do not. The EMB agar uses dyes that will inhibit growth of gram - positive bacteria (our bacteria). So going into this test, we can assume that our bacteria will test negative and therefore will not ferment lactose and / or sucrose.

Negative for lactose and sucrose fermentation

FOURTH TEST: MANNITOL SALT AGAR
It was this test that I mentioned earlier that we all got very excited over! Our bacteria finally tested positively! In this test, we determined the salt tolerance our bacteria may have. --It may or may not love salt. Only bacteria that is salt tolerant will grow on this salt agar plate. And it just so happens a positive test is common with gram - positive bacteria (our bacteria!).

Our beautiful HALOPHILE!

FIFTH TEST: MACCONKEY AGAR
Another test that is in my opinion pointless as related to our bacteria. This test is used to differentiate among gram - negative (not our bacteria) based on their ability to grow on the medium and to ferment lactose. So again, gram - positive bacteria are inhibited by the media agar (crystal violet and bile salts). If our bacteria colony is colorless, it will be negative for fermenting lactose. However, if the test shows a pink to red in color our bacteria will be positive for lactose fermentation.

Negative for lactose fermentation

SIXTH TEST: PHENYLETHYL ALCOHOL (PEA)
Today has just been a bad day for our gram - positive bacteria. This is another test that isolates gram - positive bacteria from bacteria containing a mixture of gram - positive and gram - negative bacteria. If the bacteria grows in the presence of PEA than it is a positive test and if it does not grow than it is a negative test. --Really not much different than any other test that we've run today.

Another negative test for our bacteria :(

SEVENTH AND FINAL TEST TODAY: BLOOD AGAR PLATE
In this test we see if our bacteria has the ability to lyse (destroy) red blood cells (hemolysis). There are three classifications of hemolysis-- α-hemolysis, ß-hemolysis and γ-hemolysis. In α-hemolysis, partial disruption of the red blood cells by the bacteria results in a greenish color around a colony. In ß-hemolysis, the bacteria secrete enzymes that completely dismantle the red blood cells and a clear zone appears around the bacterial colony. And in γ-hemolysis, the bacteria is nonhemolytic where it does NOT damage the red blood cells.

Our bacteria is γ-hemolytic

PICTURE DAY!