Gram-Bad Bacteria

Experimental trials were performed by students over a timeframe of three weeks to determine the identity of three unknown bacteria contained in broth medium stored in labeled test tubes that were randomly assigned containing: one Gram positive bacterium, one Gram-negative paracolon, and one Gram-negative coliform (Carson, 2016). The unknown sample assigned in this experiment was #19. After initially streaking the solution on clean streak plates and TSA agar, the identity was determined from a Gram-stain of a single, isolated colony; this was confirmed by isolation of that pure colony and viewing the pure sample in a Gram-stain under a microscope yielding a blue colored cocci morphology with no Gram-negative contamination. This was followed by Gram-negative isolation by a Gram-stain showing a myriad of Gram-negative bacillus rods, with no presence of Gram-positive. Further tests …show more content…
Tryptic soy agar (TSA) is an agar plate that allows continuous growth and nourishment of bacterial samples that are streaked and grown on it. Blood agar is a differential agar plate medium that grows gram-positive cocci bacteria, and was used to make note of hemolytic patterns (α, β, or no hemolysis) of the particular gram-positive present in the sample. MacConkey agar is a selective/ differential agar media that is selective for gram-negative bacteria, and differential between coliform and paracolon bacteria through its use of the pH indicator phenol red, bile salt detergents, and crystal violet to determine the affinity for particular gram-negative bacterium to ferment lactose (Carson, 2016). The following methods were repeated for each of the three agar plates available for experimentation during Week 1’s lab period to isolate pure, uncontaminated samples of individual