Microbiology

In the unknown lab, we started by gram-staining our unknown organism. This is a way of testing for the presence of a thick polysaccharide wall. Gram positive organisms have this thick wall, while gram negative organisms do not. To gram stain, first 4-5 drops of crystal violet are added onto the organism. Then after 60 seconds it is washed off with sterile water, and 4-5 drops of iodine is added for 60 seconds. Then hydrogen peroxide is added and left on for 10 seconds. Then 4-5 drops of safran is added for 60 seconds. Once that is done, the organism is observed under a microscope. The gram positive organisms appear purple, and the gram negative organisms appear pink. Gram negative organisms consist of non-fermenters and enteric bacteria. Gram positive organisms consist of staphococci and strepococci. Oxidase tests are done on gram negative bacteria to distunguish between non-fermenters and enteric bacteria. Positive tests appear for non-fermenters. Catalase tests are done on gram positive tests to distinguisg between staphococci and strepococci. Positive tests appear for staphococci.