Several lab experiments were performed to determine the species of an unknown culture. During staining the bacteria was determined to be gram negative after a differential gram stain was performed. The bacteria stained purple. When visualizing the bacteria, the bacteria were rod shaped and largely individuals instead of in groups. It was determined using Thioglycollate agar deep the unknown culture was inoculated using a stabbing technique, and it was determined that the bacteria is facultative.
The bacterium was also inoculated in glucose phenol red fermentation broth and lactose phenol red fermentation broth. Both tubes started red and the turned yellow if acid is present. So when the bacterium ferments it produces an acid and the phenol red turns yellow. There is also a small inverted tube that is placed inside of the tube which indicates whether gas was produced. Both tubes of glucose and lactose turned yellow as well as producing gas bubbles.
The bacterium was also tested to determine whether the bacterium could catabolize the amino acid tryptophan. To determine whether the bacterium can catabolize tryptophan a broth tube was inoculated with the unknown and cultured, and then Kovac’s reagent was added to the tube. The tube with the unknown turned red which is a positive indicator that the unknown is able to catabolize tryptophan. Two more tubes of broth were inoculated and cultured to determine if the unknown organism can ferment glucose through a mixed acid pathway or the butylene glycol pathway. In one tube the methyl-red reagent was added and in the other Barritt’s reagent B was added to the tube and then Barritt’s reagent A was added second. The first test is the methyl-red test and is looking for acid production the first tube changed from yellow to red which indicates acid production. In the second tube for the Voges-Proskauer test a pink-burgundy color is produced if the result is positive, the positive result indicates a neutral end-product. For the unknown the methyl-red was positive and the Voges-Proskauer was negative.
A test was performed on the unknown to determine if the bacterium can catabolize citrate, the medium starts green and then turns blue if the result is positive. It was determined that the unknown could not catabolize citrate.
Levine EMB agar is a selective and differential medium that allows the growth of gram negative bacteria. Gram-negative, lactose-fermenting bacteria will ferment the lactose that is in the Levine EMB plate and produce acidic products that react with the dyes that are in the plate and form colonies of different colors. The unknown culture was able to grow on the Levine EMB plate and showed a creamy pink color. On a Luisette’s agar plate the unknown was inoculated and the bacterium as exposed to UV light, on Psuedomonas species will glow under the UV light.
The unknown was also tested for motility in an agar deep tube. The tube showed a mildly positive result. The unknown was then tested for...