Lab Day 5

Teusday, day 5

Today we did a heap of inoculation.  We were curious to find out what exactly our mystery bacteria liked to snack on.  What sort of things would it eat?  (specifically, what enzymes did it have that would allow it to break down certain substances).  So, how does one solve these sorts of questions in a microbiology class?  By inoculating everything in sight, of course. 

We tested our bacteria’s appetite with all the macromolecules.  We inoculated a nutrient gelatin tube (testing for protein hydrolysis), a starch agar plate, a skim milk agar plate (testing for Casein Hydrolysis), a tributyrin agar plate (testing for triglyceride), and a DNA agar plate (testing for nucleic acids).  We also inoculated tubes filled with various sugars: Sucrose, maltose, lactose, and glucose.

  

Essentially, we set up an all-you-can-eat buffet for our lucky bacteria.  By tomorrow, we should know a little better what exactly it feeds off of, which will help immensely in identifying it.

We did, however, do a catalase test on our bacteria, to detect the presence of catalase, an enzyme that degrades hydrogen peroxide.  Hydrogen peroxide is a reactive intermediate that forms during aerobic respiration.  So, in theory, only anaerobic bacteria will not have it.  We knew perfectly well that ours was not anaerobic, seeing as it had grown in the presence of oxygen this entire time, but we tested it anyway to see the reaction.  We dropped a dilute solution of hydrogen peroxide onto our bacteria.  The results were amusing to watch.  The catalase in our bacteria quickly broke down the H2O2 into water and O2, creating rapid formation of O2 bubbles.  Ours must have had a considerable amount of catalase.