Gram Stain Test Essay

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Bacteria from the provided master stock plate were used for the gram stain test. Bacteria were then streak and grown from the master stock plate onto a working plate. After an incubation time of 24 hours at 37°C, the working plate bacteria were then used to perform the catalase and red blood cell hemolysis tests. After conducting the three tests, it was concluded that unknown #5 was Streptococcus agalactiae.

Gram Stain Test
The Gram Stain test was first performed to differentiate the bacteria based on the thickness of the peptidoglycan layer in its cell wall. The unknown bacteria appeared purple and round, therefore indicating a gram-positive cocci bacterium. The purple color was observed because S. agalactiae had a thicker layer of peptidoglycan in its cell wall, therefore it allowed for the cell wall to not be stripped away after the addition of ethyl alcohol, but rather enabled for the peptidoglycan to form pores (Madani, 2003). The pores then trapped the crystal violet-iodine complex, which produced the purple color of the bacteria cells that were observed under the light microscope.
Catalase Test
To further identify the gram positive unknown bacteria, the Catalase test was conducted in order to differentiate the gram-positive species into the Staphylococcus species (catalase-producers) or the Streptococcus species (catalase
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After allowing the bacteria to culture on the blood agar for 48 hours, clear zones of the blood agar were observed around the grown bacteria colonies. The clear zones were an indication of β-hemolysis the complete lysis of red blood cells (Savardi et al.,

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