Characteristics Of A Gram Stain Essay

1556 WordsDec 8, 20167 Pages
A gram stain is a type of differential stain, which means it allows distinction of one cell from another based on differential staining properties. The most widely used differential stain in microbiology is the gram stain. This technique separates bacteria into two groups: gram positive and gram negative. These are based on differences of the structure of the cell wall. Gram-positive cells stain purple, due to their thick peptidoglycan cell wall. Gram-negative cells will stain pink due to their thin peptidoglycan layer surrounded by a cell membrane that will not hold the crystal violet stain. After completing four different gram stains on my unknown bacteria, I found that my organism was gram negative due to the cells staining pink. I also discovered that my bacterium was rod shaped, and was in the arrangement of single cells or pairs of cells. So, this narrowed down my bacteria to be Citrobacter diversus, Escherichia coli, or Shigella sonnei since these are all gram-negative species. Kligler’s Iron Agar (KIA) Kligler’s Iron Agar can detect three primary characteristics of a bacterium: its ability to ferment lactose and glucose, its ability to produce gas from the fermentation of sugars, and the production of hydrogen sulfide (H2S). After my tube was inoculated it showed the results of completely yellow agar meaning my bacteria fermented both glucose and lactose, no bubble at the bottom meaning it produced no gas, and no black color meaning it did not ferment H2S. I was
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