What is the purpose of general growth media, selective media, and differential media? Give examples of each. General Purpose Media General Purpose media is designed to grow most organisms and do not contain growth inhibitors. Standard Methods Agar and Blood Agar Bases are examples of general purpose media. Differential Media Differential media contain a component that allow an observable change when a specific chemical reaction takes place. Simmons Citrate Agar is an example of a differential medium. In Simmons Citrate Agar, there is a pH indicator that turns from Rene to blue when citrate is utilized as the sole carbon source.
Selective Media Selective media encourage the growth of some organisms and suppress the growth of others. Dyes, antimicrobial, and salts are all examples of selective agents used for this purpose. Bile Salts are used to inhibit the growth of Gram-positive organisms on McCracken Agar. What is a pure culture? A culture in which only one strain or clone is present. It is usually derived from a mixed culture. How do you obtain a pure culture? Streak plates allow us to isolate a particular microbe from a mixed culture. Another teeth of obtaining a pure culture is the pour plate method.
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Name and describe the stages of bacterial growth. 1 . During lag phase, bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide. During the lag phase of the bacterial growth cycle, synthesis of RNA, enzymes and other molecules occurs. 2. The log phase (sometimes called the logarithmic phase or the exponential phase) is a period characterized by cell doubling. 3. The stationary phase is often due to a growth-limiting factor such as the depletion of an essential nutrient, and/or he formation of an inhibitory product such as an organic acid. . At death phase, (Decline phase) bacteria die. This could be due to lack of nutrients, a temperature which is too high or low, or the wrong living conditions. Describe the different sterilization techniques and know when to use each type. (For example, when would you use an autoclave, gas, etc? ) Sterilization is a term retiring to any process that eliminates (removes) or kills all forms of life, including transmissible agents (such as fungi,bacteria, viruses, spore forms, etc. Present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media. 1] Sterilization can be achieved by applying heat (Other heat methods include flaming, incineration, boiling, atomization, and using dry heat), chemicals, irradiation, high pressure, and filtration or combinations thereof. A widely used method for heat sterilization is the autoclave, sometimes called a converter. Autoclaves commonly use steam heated to 121-134 co (250-273 OF). To achieve sterility, a holding time of at least 15 minutes at 121 co (250 OF) at 100 kappa (15 sis), or 3 minutes at 134 co (273 OF) at 100 kappa (1 5 SSI) is required.
Ethylene oxide gas is commonly used to sterilize objects sensitive to temperatures greater than 60 co and / or radiation such as plastics, optics and electrics Nitrogen dioxide Chemical Formula: NON. Nitrogen Dioxide NON gas is a rapid and effective sterility for use against a wide range of microorganisms, including common bacteria, viruses, and spores. For the bacterial control methods described, know their mode of action. (For example, how does alcohol control the growth of bacteria?
Ozone is used in industrial settings to sterilize water and air, as well as a disinfectant for surfaces. Chlorine bleach is another accepted liquid sterilizing agent. How would you prevent the spread of a pathogen? Vaccination causes the body to produce enough white blood cells to protect itself against a pathogen. One simple way to reduce the risk of infection is to maintain personal hygiene and to keep hospitals clean. Antibiotics are substances that kill bacteria or stop their growth. They do not work against viruses because they live and reproduce inside cells.