Test Results, Boring Bacteria, and a Class Pet

Test Results, Boring Bacteria, and a Class Pet

Class: Tuesday October 8, 2013

Today we learned what our little mystery bacteria J is really made of.  And folks, it ain't much.  Last week we inoculated several different culture mediums to test the enzyme activity of Bacteria J.  

The first test was on a Starch Agar plate, with culture medium

that is made up of, well, starch.  This test was to determine if the bacteria metabolizes carbohydrates.  Our bacteria grew very well on the plate, but we want to know what it actually used for its metabolic processes.  

 

In order to determine if the starch was in fact used, we flooded the plate with iodine solution...

and then looked for a distinct halo around the bacterial colony.  Ours has a very slight halo, but not enough to be significant.  

Okay, so maybe we'll have better luck with the next test....this time we are looking to see if the bacteria metabolizes casein protein found in milk.   The results? Well, if you look really closely, you may be able to see a teeny little spot of orange. Yes, that would be our bacteria, trying to grow but failing miserably.  Poor guy.  Clearly milk protein is not his food of choice.  Let's try something else!

Casein is not the only protein available in milk; it has lactose too! Maybe Bacteria J would grow better in there! If there is any metabolic reaction with the lactose, the culture would have coagulated and formed lumpy curds throughout or even curdled into a solid.  The color also would have changed from the original lavender purple color to a pink or reddish substance.  The color did not change at all, but just to be sure no reaction took place, we inverted the tube to check the culture's consistency...

...and again got no results.  That tiny little bit of sediment at the bottom of the tube is merely from the culture components settling over the course of the week.  C'mon Bacteria J, will nothing satisfy you?!  We want to see a reaction!!  

The next culture medium we grew Bacteria J in was a triglyceride medium, to asses how the Bacteria metabolizes fats.  If it has significant metabolism of fats, then the majority of the blueness from the plate would have been 'absorbed' into the bacterial colony on the Petri dish, leaving the rest of it clear and the colony appearing dark blue/purplish.  Do we have either of these results? Take a guess.  Nope, of course not! Most of the plate is still blue and the colony is now a gross orangish-purple color.  Not enough of a change unfortunately.  

Okay, Bacteria J, you have one more chance to prove yourself! Ready?! Go eat some gelatin!! In this test we inoculated a test tube with a gelatin culture medium to asses how the bacteria metabolizes, well, gelatin.  If it does, then the once-semi-solid tube of culture should be mostly liquified, even after refrigeration.  But no, our culture stayed nice and semi-solid like, meaning no metabolism of gelatin here.  Of course.  

Well, despite the abysmal performance by Bacteria J in the realm of metabolic functions, we did have one highlight to the class.  World, meet Striker, our little class pet.  

And you thought stink bugs were gross!