Agar is an excellent hardening agent because most microorganisms cannot degrade it. Microbes growing on agar medium can be incubated at a wide range of temperatures. After being melted in boiling water, it can be cooled to a temperature that is tolerated human hands as well as microbes. It melts at about 100C but once melted does not harden until it reaches about 50C. Why is agar superior to gelatin as a solidifying agent for bacterial culture media? Few microbes can degrade agar, is not usually decomposed microorganisms causing it to remain as a does not melt at room temperature. flaming wire loop) UV Radiation (prevents replication and to surface sterilization because it does not penetrate glass, dirt films, water and other for water treatment) Ionizing Radiation (gamma radiation penetrates deep into objects, destroys endospores but not always effective with viruses, used for sterilization of food, plastic, disposable supplies) Phenolics (laboratory and hospital disinfectants, denatures proteins and disrupts cell walls) Alcohols (disinfectants and antiseptics, kills bacteria and fungi but not spores) Halogens Heavy Metals (effective but toxic) Aldehydes Sterilizing Gases 3.
Sterilization: destruction or removal of all viable organisms Disinfection: killing, inhibition or removal of disease causing organisms Sanitization: reduction of microbial population to levels deemed safe public health standards Antisepsis: prevention of infection of living tissue microorganisms (inhibit growth) Methods of Sterilization Filtration (reduces microbial population or sterilizes materials removing microorganisms) Steam Sterilization (carried out above 100c which requires saturated steam under pressure aka effective against all types of microorganisms including spores!!) Moist Heat (destroys viruses fungi and will not destroy spores and does not sterilize) Pasteurization (controlled heating at well below does not sterilize but does kill pathogens present and slow spoilage reducing total load of organisms present Dry Heat Sterilization (less effective than moist heat sterilization requiring higher temps and longer exposure oxidizes cell constituents and denatures proteins) (Used for things that might be damaged moist heat or are impenetrable moist heat like sharp instruments, powders and petroleum products) Dry Heat Incineration (e.g. Be sure to include limitations and advantages of each type. Be prepared to discuss the various methods of sterilization. His data was weakened further the discovery of oxygen oxygen was soon shown to be essential for the growth of most organisms. The supporters of spontaneous generation responded that heating the air in sealed flasks destroyed its ability to support life, and therefore did not discredit the theory of spontaneous that he excluded the when he sealed the vessels from the air. He proposed that air carried germs to the culture medium but also commented that external air might be required for growth of animals already in the medium. He found that no growth took place as long as the flasks remained sealed. Flask 1 was left open Flask 2 was sealed Flask 3 was boiled and then left open Flask 4 was boiled and then sealed Flask 1: turned cloudy and microbes were found Flask 2: turned cloudy and microbes were found Flask 3: turned cloudy and microbes were found Flask 4: did not turn cloudy and microbes not found He sealed glass flasks that contained water and seeds and then placed the flasks in boiling water for about 45 minutes. from Spallanzani put broth into four flasks. Spontaneous Generation: the idea that organisms originate directly from nonliving matter. What causes microbes to form in decaying broth? Hypothesis: microbes come from the air. What is a practical application of experiments performed the Italian naturalist Lazzaro Spallanzani in the 18th century? On what grounds were experiments with hermetically sealed flasks criticized proponents of spontaneous generation? Lazzaro Spallanzani: one of the first to disprove spontaneous proved microorganisms could be killed boiling.
0 kommentar(er)
