Name:____Hannah Pie______Lab Section: ____501_________
Unknown Number: ___30____
Data Table and Results Analysis:
Unknown Bacteria Name Gram Stain Cell Morphology and
Arrangement Carbohydrate Fermentation Pigment (Color) Streak Plate Successful
Glucose
(color) Lactose
(color) Sucrose
(color) Salmonella enterica
serovar Typhi expected negative r AG – – no Salmonella enterica
serovar Typhimy results Gram negative
(pink) bacilli (rod)
single cells acid, with gas
(yellow) No fermentation
(pink) No fermentation
(orange/red) none
(tan/ white) yes
My unknown bacteria is Salmonellna enterica serovar Typhi. When the provided Gram stain images, I determined that my bacteria was Gram negative as the bacterial cells appeared pink. The cells on the provided image appeared to be bacilli in shape and were mostly found as single cells. The only sugar that was observed to be fermentable by my bacteria was glucose, which resulted in a yellow color within the phenol red broth tube due to the acidic products from fermentation. One result from the provided image that was slightly different than the expected result was that the lactose tube was pink in color rather than staying orange/red. This likely meant that the bacteria broke down the peptones in the broth to make the solution more alkaline. The provided image showed a successful streak plate as there were visible individual colonies. Those colonies did not have a pigment as they were tan/white in appearance. The observable colony morphology for S. enterica serovar Typhi was circular cells with entire margins. They appears slightly convex, but it was difficult to tell from the provided image. Discussion:
The method I used to determine which bacteria I had was by comparing my results with the expected results from the unknown bacteria key. Being a Gram negative bacteria, I could rule out all the Gram positive bacteria leaving me four Gram negative options to examine further. As Serratia marcescens is cocci or coccibacilli, I could rule out that bacteria as well. As both Escherichia coli, Pseudomonas aeruginosa, and S. enterica serovar Typhi are all single cell bacilli, I had to look at the pigment and fermentation results to determine which bacteria I had. The fermentation results a for both E. coli and P. aeruginosa did not match my results. E. coli should have fermented all three sugars, while P. aeruginosa would not have fermented glucose. The fermentation results I obtained did match that of S. enterica serovar Typhi leading me to determine that S. enterica serovar Typhi was my unknown bacteria. Additionally, my lack of pigmentation also matched the expected results of S. enterica serovar Typhi.
S. enterica serotype Typhi are non-spore forming, motile bacteria that are facultative anaerobes (Giannella, 1996). Salmonella bacteria are considered enteric, meaning they are commonly found within the digestive tract of humans. Unlike other species and serotypes of Salmonella, humans are the only host species for S. enterica serotype Typhi (Giannella, 1996). S. enterica serotype Typhi causes the potentially life-threatening disease typhoid fever within humans. The typhoid fever is most often transmitted through water or food that has been contaminated with the fecal matter of other infected individuals or those who serve as carriers (CDC, n.d.).
Work Cited:
Center for Disease Control and Prevention (n.d.). Typhoid Fever and Paratyphoid Fever – Information for Health Care Professionals. Retrieved from https://www.cdc.gov/typhoid-fever/health-professional.html.
Murphy, R.A. (1996). Salmonella. In S. Baron (Ed.), Medical Microbiology(Chapter 31, 4th ed.). Galveston (TX): University of Texas Medical Branch at Galveston. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK8435/.
