Identification Of Unknown Bacteria 91090 As Pseudomonas Fluorescens
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Identification of Unknown Bacteria 91090 as Pseudomonas fluorescens
The unknown sample, number 91090, is more than likely a sample of Pseudomonas fluorescens. I concluded that this sample was Pseudomonas fluorescens through a series of observations and tests to determine morphological and physiological characteristics.. A differential staining test was the first test performed that utilized the sequential application of a primary stain, decolorizing reagent, and a counterstain. An isolated colony of the unknown sample derived from a T-streak was smeared onto a clean microscope slide. The primary stain, crystal violet, was then applied to the bacterial specimen. Crystal violet is a basic stain that posses a positive charge that attracts the negative charge of bacterial cell walls and nucleic acids ultimately staining the cells blue. The primary stain either remains or is washed away from the cell when exposed to the decolorizing reagent, alcohol. The final step of the differential staining process is the application of the counterstain, safranin, that stains the cell wall of bacteria that did not retain the primary stain. The visualization of the microbial organism under a microscope revealed the cells of the unknown sample were stained pink indicating it is a Gram-negative bacteria. The primary stain does not adhere to Gram-negative bacteria due to the thin layer of peptidoglycan within the cell wall that is washed away during the process of decolorization thus allowing for the safranin to stain the cell again. The physical shape of the cell was easily distinguishable as a bacillus or rod-shaped bacteria matching the characteristics of P. fluorescens.
The next test performed on unknown sample 91090 was the MacConkey plate test, ...
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... a flagella stain or litmus milk reaction. A flagella stain is performed through exposing a slide of the organism with a dye to stain the cell itself then a silver compound or other heavy metal to coat the flagella. Once observed under a light microscope, the flagella of the P. fluorescens will be able to be viewed where they previously would not be due to their original thickness. A litmus milk test uses a medium that contains 10% powdered skim milk and a small amount of litmus (Brown 2010). This test aids in the understanding of whether or not a microorganisms would be capable of fermentation. The solution along with the unknown bacteria is placed in a tube incubated for 4 to 5 days but observed every 24 hours. The results of P. fluorescens would display some protein hydrolysis but would also be masked to some degree by the soluble pigment produced by Pseudomonas.