Microbiology

In the unknown lab, we started by gram staining our 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 for 10 seconds. Then 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.