【正文】 er able to survive. Antimicrobials have a range of cellular targets, with the agents that are least selective in their targeting tending to be effective against the widest range of microbes. ? The cellular targets of physical and chemical agents fall into four general categories: 1. the cell wall. 2. the cell membrane. 3. cellular synthetic processes (DNA,RNA), and 4. proteins. The Effects of Agents on the Cell Wall ? The cell wall maintains the structural integrity of bacterial and fungal cells. Several types of chemical agents damage the cell wall by blocking its synthesis, digesting it, or breaking down its surface. A cell deprived of a functioning cell wall bees fragile(脆弱的 ) and is lysed（溶解） very easily. How Agents Affect the Cell Membrane ? All microanisms have a cell membrane posed of lipids and proteins, and we learned in previous chapter, a cell’ s membrane provides a twoway system of transport. If this membrane is disrupted, a cell loses its selective permeability（透過性 ） and can neither prevent the loss of vital molecules nor bar the entry of damaging chemicals. Agents That Affect Protein and Nucleic Acid Synthesis ? Microbial life depends upon an orderly and continuous supply of proteins to function as enzymes and structural molecules. As we saw in chapter 9, these proteins are synthesized on the ribosomes through a plex process called translation. For example, the antibiotic choramphenicol（氯霉素） binds to the ribosomes of bacteria in a way that stops peptide bonds from forming proteins required in growth and metabolism and are thus inhibited from multiplying. ? The nucleic acids are likewise necessary for the continued functioning of microbes. Some agents bind irreversibly to DNA, preventing both transcription and translation。 C for Overnight Inducing Spore(芽孢 ) Germination Sterilized Medium Repeat the Cycle Several Times Flow of Tyndallization Normal Autoclaving （常規(guī)高壓滅菌） Continuous Autoclaving （連續(xù)高壓滅菌） High Pressure Autoclaving(滅菌 ) An autoclave（滅菌器） is a pressureized（壓力的） device designed to heat aqueous(含水的 ) solutions（溶液） above their boiling point（沸點） at high atmospheric pressure to achieve sterilization . Autoclave Old Style Autoclave Modern Autoclave （高壓滅菌器） Normal Materials: 121 176。 C for 30 minutes 138 176。 enveloped viruses。Chapter Overview ? The control of microbes in the environment is a constant concern of health care and industry since microbes are the cause of infection and food spoilage(破壞 ), among other undesirable events. ? Antimicrobial control is acplished using both physical technique and chemical agents to destroy, remove, or reduce microbes in a given area. ? ? Many factors must be contemplated（關(guān)注） when choosing an antimicrobial technique, including the material being treated, the type of microbes involved, the microbial load, and the time available for treatment. ? Antimicrobial agents damage microbes by disrupting the structure of the cell wall or cell membrane ,preventing synthesis of nucleic acids （ DNA and RNA） , or altering the function of cellular proteins . Microbicidal agents kill microbes by inflicting nonreversible（不可逆的） damage to the cell .microbistatic agents temporarily inhibit the reproduction of microbes but do not inflict irreversible damage .Mechanical antimicrobial agents physically remove microbes from materials but do not necessarily kill or inhibit them. ? Heat is the most physical agent in microbial control and can be delivered in both moist (steam sterilization, pasteurization) and dry forms. ? Radiation exposes material to high energy waves that can enter and damage microbes. Examples are ionizing and ultraviolet radiation. ? Chemical antimicrobial are available for every level of microbial treatment, from lowlevel disinfectants to highlevel sterilants. Antimicrobial chemical include halogens, alcohols, phenolics, peroxides, heavy metals, detergents, and aldehydes. Controlling Microanisms ? Controlling our degree of exposure to potentially harmful microbes is a monumental（非常的） concern in our lives, and it has a long and eventful（重大的） history. GENERAL CONSIDERATIONS IN MICROBIAL CONTROL ? The methods of microbial control belong to the general category of decontamination（凈化） procedures, in that they destroy or remove contaminants. Most decontamination methods employ either physical agents, such as heat or radiation, or chemical agents such as disinfectants and antiseptics（無菌的 ） . RELATIVE RESISTANCE OF MICROBIAL FORMS ? The primary targets of microbial control are microanisms capable of causing infection or spoilage that are constantly present in the external environment and on the human body . ? This targeted population is rarely simple or uniform。 fungal spores and hyphae。 C for 2 Hours. Pasteurization (巴氏消毒法 ) Louis Pasteur (December 27, 1822 – September 28, 1895 ) Louis Pasteur was a French chemist and microbiologist best known for his remarkable breakthroughs in the causes and prevention of disease. Conception of Pasteurization The heating of every particle of milk or milk product to a specific temperature for a specified（特定的） period of time. Aim:Heating liquids for the purpose of destroying bacteria, protozoa（原生動物） ,molds（霉菌） , and yeasts（酵母） . Pasteurization System 巴氏消毒系統(tǒng) The Structure of Pasteurizer Pasteurization HIgh Temperature/Short Time(超高溫瞬時滅菌 HTST) Low Temperatur