To begin, a streak was performed on two TSA plates and a blood agar plate using the three-sector streak technique from the unknown culture tube to isolate the two unknown bacterial colonies. The plates were then incubated for 12 hours at 37 ̊C. The blood agar plate was used to create a greater contrast in color to help distinguish between bacterial colonies by size and color. Two distinct colonies could be seen growing on the blood agar plate shown in figure 1. The smaller, opaque colored bacterial colonies were labeled “A” and the larger, more transparent bacterial colonies were labeled “B”.
After observing the different colony growth, isolation streaks were performed on TSA plates for both bacteria A and B using the three-sector streak …show more content…
Once the Gram stains were complete, each sample was looked upon under a microscope as seen in figures 3 and 4. Bacteria A was found to be Gram-negative (fig. 3) due to displaying a predominately red color. Bacteria B was found to be Gram-positive (fig. 4) due to displaying a dominate blue color. Bacteria B was also noticeably a rod, or bacillus, shape which helped to further narrow down the possibilities to two bacteria: Bacillus cereus, and Bacillus …show more content…
A yellow color change in the lactose fermentation broth would signal a positive result. Bacteria A was able to ferment lactose and displayed a yellow color change as seen in figure 6. Along with the lactose fermentation test, a MacConkey plate streak was performed. This test was not necessary, but it is used to select for Gram-negative bacteria, and can also indicate lactose fermentation. The MacConkey test can be seen in figure 6, however, the results lactose fermentation results are not easily seen on the MacConkey’s plate. These two tests narrowed the bacteria down to three choices: Citrobacter freundii, Enterobacter aerogenes, and Escherichia
After observing the different colony growth, isolation streaks were performed on TSA plates for both bacteria A and B using the three-sector streak …show more content…
Once the Gram stains were complete, each sample was looked upon under a microscope as seen in figures 3 and 4. Bacteria A was found to be Gram-negative (fig. 3) due to displaying a predominately red color. Bacteria B was found to be Gram-positive (fig. 4) due to displaying a dominate blue color. Bacteria B was also noticeably a rod, or bacillus, shape which helped to further narrow down the possibilities to two bacteria: Bacillus cereus, and Bacillus …show more content…
A yellow color change in the lactose fermentation broth would signal a positive result. Bacteria A was able to ferment lactose and displayed a yellow color change as seen in figure 6. Along with the lactose fermentation test, a MacConkey plate streak was performed. This test was not necessary, but it is used to select for Gram-negative bacteria, and can also indicate lactose fermentation. The MacConkey test can be seen in figure 6, however, the results lactose fermentation results are not easily seen on the MacConkey’s plate. These two tests narrowed the bacteria down to three choices: Citrobacter freundii, Enterobacter aerogenes, and Escherichia