After gram staining both the gram positive and gram-negative bacteria, the groupings were observed. For the unknown gram-positive bacteria, the cells were arranged in a cocci cluster, while in the gram-negative bacteria, the cells were arranged in a rod cluster. Both the gram negative and gram-positive bacteria exhibit a small yellow colony on the TSA plate. After 48 hours, the MSA plate was observed. Individual isolated colonies were found throughout the plate, with a yellowish color. The medium also changed from a reddish color to a yellowish color, indicating that the unknown gram-positive bacteria was successfully able to ferment mannitol. This changing of color could be observed due to the fact that MSA uses the pH indicator phenol red,
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However, the indole test from the SIM test, citrate test, and the growth of the EMB plate was deemed to be the most important test because the unknown bacteria was tested positive for indole, negative for citrate, and had metallic green sheen, with purple and black centers on it. This indicates that unknown 18 for the gram-negative bacteria was in fact E. coli since no other bacteria shared the same results. This indication was further confirmed by both the (-) in sulfur reduction, the (+) in the Methyl Red test, (-) in the VP test, the pink to reddish growth in the Macconkey agar, and (-) in the urease test. For the unknown gram-positive bacteria, the positive result of the bile esculin test indicates the unknown gram-positive bacteria for number 18 was indeed S. aureus. This was then confirmed again by the grouping of the cell morphology (arranged in cocci cluster), the colony morphology (small pale colonies), the (+) reaction in the catalase test, as well as the (+) result for being able to ferment mannitol in the MSA plate …show more content…
aureus is a common pathogenic, gram positive bacteria found throughout our environment. Even so, S. aureus can be very dangerous and is often the main culprit that causes food poisoning, therefore making it important to study upon it. Once colonization of S. aureus occurs in the human host, it can cause serious infections, toxinoses, and life threatening disease such as skin and soft tissue infections, toxic shock syndrome and septicemia. Due to this, scientist are starting to used natural antimicrobials to improve the quality and shelf life of food to prevent food poisoning, from S. aureus from occurring. One of these antimicrobial is Nisin, which is a peptide produced by strains of Lactococcus lactis subs. latis. It has the ability to kill of bacterial cell by interfering with their basic energy transduction at the cytoplasmic membrane (Xingchen, et. al
However, the indole test from the SIM test, citrate test, and the growth of the EMB plate was deemed to be the most important test because the unknown bacteria was tested positive for indole, negative for citrate, and had metallic green sheen, with purple and black centers on it. This indicates that unknown 18 for the gram-negative bacteria was in fact E. coli since no other bacteria shared the same results. This indication was further confirmed by both the (-) in sulfur reduction, the (+) in the Methyl Red test, (-) in the VP test, the pink to reddish growth in the Macconkey agar, and (-) in the urease test. For the unknown gram-positive bacteria, the positive result of the bile esculin test indicates the unknown gram-positive bacteria for number 18 was indeed S. aureus. This was then confirmed again by the grouping of the cell morphology (arranged in cocci cluster), the colony morphology (small pale colonies), the (+) reaction in the catalase test, as well as the (+) result for being able to ferment mannitol in the MSA plate …show more content…
aureus is a common pathogenic, gram positive bacteria found throughout our environment. Even so, S. aureus can be very dangerous and is often the main culprit that causes food poisoning, therefore making it important to study upon it. Once colonization of S. aureus occurs in the human host, it can cause serious infections, toxinoses, and life threatening disease such as skin and soft tissue infections, toxic shock syndrome and septicemia. Due to this, scientist are starting to used natural antimicrobials to improve the quality and shelf life of food to prevent food poisoning, from S. aureus from occurring. One of these antimicrobial is Nisin, which is a peptide produced by strains of Lactococcus lactis subs. latis. It has the ability to kill of bacterial cell by interfering with their basic energy transduction at the cytoplasmic membrane (Xingchen, et. al