Lab Exam 2 Review: Exercise 19: What are staphylococcus and streptococcus? Difference between them. Test to differentiate them. Role of catalase Effect of hydrogen peroxide on other bacteria Disease caused by staphylococcus aureus Definitive test for S.aureus Role of coagulase Exercise 20: Expand IMViC This can be used only for enteric bacteria Role of tryptophanase Kovac reacts with indole to produce rose color. Test to identify the presence of tryptophanase in a medium. Composition of MRVP media Methyl red test is for: Acidic end products of fermentation lowers the pH of the media. Voges-Proskauer: Few bacteria produce end products such as ethanol and 2,3 butanediol. KOH and alpha Naphtol react with acetoin (precursor of 2,3 butanediol) to produce pink or red color. Enteric bacteria can never show both MR and VP negative test. Citric acid – produced by citric acid cycle. Citrate test used to identify the production of citrase enzyme. Role of citrase Composition of simmon’s citrate agar. When does BTB turns royal blue? Exercise 21: Role of urease Proteus can be differentiated from other enteric bacteria by their urease activity. Importance of urease ecologically Broth used for urease test Positive test for urease Exercise 22: At birth mucous membrane is sterile. First invaders of mouth and throat S.mutans appears when teeth arise and disappear as the teeth