国外微生物学基础实验(五 )-英文版.pptVIP

Getting Ready for Today’s Lab Get your lab card (back counter). Get your plastic tub of materials. Turn on microincinerator. Have your lab coat ion and goggles, Lab #5 and lab card on bench next to you. TURN IN: Pre-lab #5 and Lab Report #4. End of Today’s Lab You may turn in your dirty copy of Lab #5 to save for use next week. Next week bring a clean and dirty copy of Lab Report #6. Lab Report #5 is due next week, as well as Pre-lab #6. Microbial Control Laboratory 5 Action of Antimicrobial Agents Many types of chemical and physical microbial controls Modes of action fall into two basic categories 1. Alteration of cell walls or cytoplasmic membranes 2. Interference with protein and nucleic acid structure Alteration of Cell Walls and Membranes Cell wall maintains integrity of cell When disrupted, cannot prevent cell from bursting due to osmotic effects Cytoplasmic membrane contains cytoplasm and controls passage of chemicals into and out of cell When damaged, cellular contents leak out Viral envelope responsible for attachment of virus to target cell Damage to envelope interrupts viral replication Nonenveloped viruses have greater tolerance of harsh conditions Damage to Proteins and Nucleic Acids Protein function depends on 3-D shape Extreme heat or certain chemicals denature proteins Nucleic Acids can be damaged or destroyed by chemicals, radiation, and heat. Can produce fatal mutants Can halt protein synthesis through action on RNA Relative Susceptibility of Microorganisms Protocol for Testing a Control Agent The basic principle for testing any control agent, (whether temperature, chemical or antibiotics) is always the same: 1. Expose the organism to the agent. 2. Remove the agent. 3. Put the organisms in favorable growth media. 4. Look for reproduction of organisms. Methods of Microbial Control That We Will Be Examining Today Physical Heat UV Chemotherapeutic Antimicrobic drugs, like antibiotics Chemical Bleach, other chemical