Lab Report On Unknown Mixed Culture

Introduction

The purpose of this project was to detect which organism we had in our unknown mixed culture tube by running a series of experiments to detect which specific Gram negative organism we had. To detect your gram positive from the mixed culture was given as extra credit points also. A Gram stain was performed and isolation streak plate in order to isolate and observe the unknown organism. Before the series of test, a dichotomous key had to be written up in order to know what steps and tests to run to identify the unknown Gram negative organism. I had to run three experiments in all before I identified my unknown. Identifying unknown organisms is really important, one reason is because it produces benefits for many aspects of
My dichotomous key was the “key” thing to finding my unknown out. After the gram staining of the gram negative, the O-F test was the first test to start my process off; it produced yellow through out both tubes. This meaning it is a fermentor of glucose and can be oxidative of glucose. It is also considered O-F because the mineral oil is added to one to promote an anaerobic growth and fermentation, while the one w/o oil is for oxidation and aerobic growth and it grew well in both. After finding out I had a fermentor the second thing was to do perform an Indole production experiment in order to cut my chances of finding my unknown in half. The Indole production test was recorded as negative. It is observed as negative because after adding the Kovac’s reagent there was no color change. Kovac’s reagent added to the tube reacts with DMABA and with any Indole present and produces a compound that turns the reagent layer pink. No color change for an Indole Production means tryptophan is not broken down into Indole and Pyruvate. After finding out I was negative for Indole, looking at my key my next test was Phenol Red Arabinose which also put me at a four to two ratio for finding out my unknown. After performing this test I found out this test is also negative. I recorded this test as negative because there was no color change in the tube meaning no reaction/no fermentation. Phenol Red Broth is a differential medium which also has a carbohydrate added. Phenol red and peptone are included in the medium as ph indicators; an indicator of gas production called Durham tube is also added. When the pH is raised it turns the tube pink, when lowered it turns it yellow and a bubble would mean gas production. After finding out I was negative for Arabinose test I was really excited because that left me with