MCB 100 1st Edition Lecture 23 Outline of Last Lecture I. MutationsII. Genetic recombinationIII. Three ways for bacterial DNA to move from a donor strain to recipient strainIV. Three ways bacterial DNA can survive if it is an autonomous replicon V. Regulation of gene expression in bacteriaVI. Recombination of DNA technology (Chapter 8) Outline of Current Lecture I. What is the difference between bacteriocidal and bacteriostatic? II. Factors that affect efficiency of a bacteriocidal treatment a. Speciesb. Material c. Biological factorsd. Environmental factors Current LectureI. What is the difference between bacteriocidal and bacteriostatic? a. Bacteriocidal agent- a physical or chemical treatment that will kill bacteriab. Bacteriostatic agent- a physical or chemical treatment that will prevent the growth of bacteria, but will not kill them (static = stays the same) c. Why would anyone want to use a bacteriostatic agent instead of a bacteriocidal agent?i. Bacteriostatic agent/treatment may provide adequate protection of the product from bacteria without destroying the productii. Conditions needed to kill bacterial endospores are so harsh that they may damage the product that you want to protect from the bacteria! (ex. Incineration kills bacteria but it is not a very good way to preserve meat)iii. Adding salt or spices or drying meat is bacteriostatic, it will stop or slow bacterial growth on the meat--> slows spoilage without destroying the meat iv. Refrigeration = bacteriostatic! I. Factors that affect efficiency of a bacteriocidal treatment a. What is the species of microorganism that you are most worried about? i. Maybe you don't have to kill every species of bacteria in a sample in order to achieve the desired effect. Some species of bacteria are easier to kill than others (easiest to kill = enveloped microorganisms and those with gram-These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.positive cell walls, since gram-negative bacteria has a double membrane; hardest to kill = endospores!) b. What is the material that needs to be protected from microorganisms?i. A process that sterilizes a metal instrument may be too harsh to use on food or plasticii. A procedure that works for preservation of one type of food may be inappropriate for anothera. Biological factors that affect the efficiency of a sterilization procedure:i. Age of the cells that you want to killii. Size of the population of bacteria that you want to get rid of b. Environmental factors that affect efficiency of a sterilization or preservation procedure: i. Storage temperature of the productii. pHiii. Water activity (osmotic pressure)iv. Presence of organic
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