The experiment employed the results from streak plating on TSA agar, endospore staining, gram staining, and outside research to establish the identity of the unknown bacteria sample, Swiss, to be Proteus vulgaris.Today, there is a constant debate in society about microorganisms, thus making it essential to determine their identities. Establishing the microorganisms’ identities is vital because it helps scientists figure out what agent is causing a specific disease and which microbes are beneficial to humans. The objective of this experiment is to identify an unknown bacterium by applying all tests previously learned and conducted in the microbiology lab classes.The unknown utilized in this experiment was identified as Swiss.
Endospore staining, streak plating on TSA agar, and gram staining were conducted on the unknown sample. The first test performed was the streak plate test on the TSA agar. The method used was the quadrant method, where an inoculating loop was used to transfer the culture to the TSA agar. After the TSA agar was incubated for 48 hours at 37 Celsius, a gram stain was performed. Then, an endospore stain test was conducted on the unknown bacteria. Instead of using a steaming apparatus during the endospore staining process, a Bunsen burner was held under a ring stand..
All procedures were followed from the laboratory outlines found in Microbiology: Laboratory Theory and Application {Leboffe and Pierce 2015).To begin the identification process, an unknown sample, Swiss, S. epidermidis, and E. coli, underwent a gram stain. S.
epidermidis was used as the gram-positive control while E. coli was used as the gram-negative control. The unknown sample appeared as a gram-positive bacteria. S. epidermidis provided a control of a cocci bacteria sample, and the E. coli produced a control of a rod bacteria sample. The unknown bacteria resembled a rod shape.
Figure 1 is a picture of the sample after undergoing the gram staining process. The second test performed determined if the unknown sample contained an endospore. The negative control, E. coli, was determined to be non-sporing while the positive control, B. megaterium, was determined to be spore positive. The unknown sample was determined to be non-sporing.
The table below summarizes the results from the gram staining and the endospore staining process. The cell morphology of the unknown sample appears as rod-shaped, smooth, and convex.The results from the gram stain indicated that the unknown sample was a gram-negative rod bacteria. E. coli was pink and rod-shaped while the unknown was peach and rod-shaped. The gram staining test showed that there was a difference between E. coli and the unknown sample, Swiss. This may have occurred because the unknown sample could have been contaminated beforehand or the gram staining process was incorrectly performed.
The endospore stain indicated that the unknown sample was not a sporing bacteria due to the lack of green dots within the rod cells. The dichotomous key in Figure 2 shows that based on the results from the two stainings, the unknown sample was either Serratia marcescens, Proteus vulgaris, or Shigella sonnei. Observing the gram stain in Figure 1, the colonies of the unknown sample appear to be more chain-like than cluster-like. When examining the gram stains of Serratia marcescens and Shigella sonnei, it was noticed that the colonies were in clusters. However, when comparing the unknown sample’s gram stain to gram stains of Proteus vulgaris, they share the most similarities because they both appear chain-like, have similar shapes, and have almost the same color. Based on available data, it was concluded that the most likely identity of Swiss was Proteus vulgaris.
To have a more accurate prediction of the unknown sample, performing a capsule stain can give more valuable information. Repeating the gram stain and endospore stain process may also make it less challenging to identify the unknown sample.
