The following week, we conducted three tests. Initially, we inoculated an enterotube to determine the identity of our unknown …show more content…
First the SIM test showed that the unknown is motile but is negative for sulfide and indole production. Next, I concluded that my unknown has the ability to reduce nitrate into nitrite using nitrate reductase. Thirdly, the milk agar plate T-streak remained white meaning that the unknown lacks proteases which convert casein into a transparent derivative. The next test determined that my unknown is positive for catalase. Lastly, the oxidase test resulted in a negative reaction. Meaning that my unknown is not an oxidase-producing microbe.
Using Appendix E of the General Microbiology Laboratory lab handbook, I narrowed down the unknown microorganism to Enterobacter aerogenes. Every test matched with my experimental results except for the fermentation of lactose. According to Appendix E, E.aerogenes is able to ferment lactose however my enterotube experiment yielded a negative result. I assume this difference is due to human error of misidentification of the color of the enterotube chamber. Besides, the MacConkey plate yielded a result of red microbial growth meaning that my unknown has the ability to ferment