Catalase and Sugar Iron Test

    This week our endeavor in determining the identity of our soil microbe continued as we employed two new microbial techniques, the catalase and sugar iron test. Catalase is an enzyme that breaks hydrogen peroxide into water and oxygen. Many kinds of bacteria have evolved to produce catalase because hydrogen peroxide can be deadly within a cell. The catalase test determines whether or not a strain of bacteria produces catalase by exposing a colony of bacteria on a microscope slide to hydrogen peroxide and observing whether or not oxidization, or bubbling, occurs. Microbes that are catalase-positive are deemed Micrococcaceae and catalase-negative are deemed Streptococcaceae. Our particular soil microbe did not express any catalase activity. After employing the catalase test on our microbe many times, we continued to not observe any bubbling or activity. This suggests that our microbe is under the catalase-negative Streptococcus group. 

   

    The triple sugar iron test determines carbohydrate fermentation and hydrogen sulfide production. The agar gel changes color in presence of different fermenting abilities and gas production allowing the researcher to differentiate a microbes decease of their abilities. One of our controls acted as planned. The E. Coli tube reaction was over acid, indicating fermentation, and produced a yellowish color in the agar. However, our P. vulgarism  control tube did not produce the desired reaction. In the butt of the tube, the bacteria did not produce stable-acid end products which produces a black precipitate at the bottom of the tube. Our unknown soil microbe appears to be a glucose, sucrose, or lactose fermenter because it tinted the entire tube a yellowish color similar to our control subject, E. Coli. There was no precipitate at the bottom of the tube indicating there was no hydrogen sulfide production. This means our soil microbe has carbohydrate fermenting abilities. Below are pictures of our control groups and soil microbe.

     According to our tests this week, our soil microbe should be Streptococcaceae and have the ability to ferment different carbohydrates. It was catalase-negative and did not produce hydrogen sulfide or gas. I believe this indicates that this bacteria is under the genus Enterococcus faecalis or Streptoccocus spp. This is because the microbe was a facultative anaerobe because it utilized the glycolosis pathway anaerobically and aerobically meaning it is specific to air conditions. These two groups are also very likely because our bacteria is gram positive and cocci-shaped. However, this does contradict previous hypotheses that our bacteria could be under the genus  Listeria monocytogenes because of its non-acid fast characteristic.