September 27th, 2011
Today my goal was to determine whether the environmental and unknown samples were Gram-positive or Gram-negative. After using the Aseptic technique to transfer the bacteria to their designated slides, I first stained them with crystal violet for 20 seconds to determine if they were Gram-positive. After rinsing off excess dye, I used Gram’s iodine and rinsed it off after a minute. I squirted ethanol on the slide at a 45 degree angle to see if the stain would stay or not, and it stayed for my unknown. I then used safarin on both for about a minute then rinsed them off and examined the slides using a microscope. My environmental is Gram-negative because the iodine decolorized the crystal violet and safarin and my unknown was Gram-positive because it was not decolorized by Gram’s iodine.
Environmental
Unknown
September 29th, 2011
My next goal was to determine whether my environmental and unknown had capsules or not protecting them. To do this I used the Aseptic technique to transfer my samples to drops of nigrosin situated on their respective slides before spreading it on the entire slide. I then drenched the slide in crystal violet and let it sit for 20 seconds before rinsing it off and examining the smears. The environmental did not have a capsule but there seemed to be no bacteria on the unknown slide. I made a new slide only to realize when I examined it that there were capsule bacteria and non-capsule bacteria which meant there was a cross-contamination in my sample. I prepared a third slide only to realize I could not see anything due to the dye being too dark. I changed my procedure a bit by using safarin and clearly saw that my unknown had no capsule.
Unknown
