tailieunhanh - Lab Exercises in Organismal and Molecular Microbiology_2

When students move from the lecture hall to the microbiology laboratory, they need help bridging the gap between the theory and the practice of what they are learning. The equipment is unfamiliar, the procedures are unfamiliar, and many of the materials they are handling are unfamiliar. Linking the information from their classroom lectures to the laboratory procedures is necessary for their ultimate success. Our goal for this laboratory manual is to provide the bridge that helps students integrate their classroom lectures with their laboratory experiences. This integrated approach is the only way to ensure understanding and mastery in microbiology | Alexander-Strete-Niles Lab Exercises in Organismal and Molecular Microbiology The McGraw-Hill Companies 2003 VI. Controlling the Risk and Spread of Bacterial Infections 27. Killing Bacteria with High Temperature EXERCISE 27 Killing Bacteria with High Temperature Background Dry and Wet Moist Heat Heat is one of the most effective methods used to kill bacteria. Heat is generally divided into dry and wet moist heat table . Dry heat which includes incineration and the hot-air oven kills bacteria by oxidizing components of the cell. Wet moist heat which includes boiling water autoclave pressure cooker pasteurization and fractional sterilization kills bacteria by coagulating proteins in the cell including essential enzymes and cell structures. Using Dry Heat in the Kitchen Dry heat is used for grilling on the stovetop or baking in the oven. When properly used dry heat in the kitchen can effectively eliminate the risk of contracting certain types of bacterial diseases. Pathogenic strains of Escherichia coli such as the 0157 H7 strain cause diarrhea and can be contracted by eating undercooked hamburger. Cooking hamburger meat to a temperature of 80 C or above should kill all vegeta tive cells of E. coli if present. Likewise species of Salmonella such as S. enteritidis and S. typhimurium are associated with eating undercooked chicken and eggs causing salmonellosis. The thorough grilling or baking of chicken and eggs to a temperature of 80 C or above should kill all vegetative cells of Salmonella if present. Using Wet Heat in the Kitchen Boiling water has been used for a long time around the home in cooking and disinfecting items such as baby bottles and canning jars. Drinking water may also require boiling on occasion. For example whenever water flow is interrupted in water lines by a rupture or drop in pressure there is a chance of bacterial contaminants entering the water supply. In these cases city officials may advise people to boil their water prior to use. This .