Radiation Microbiology

Radiation Microbiology - the branch of Microbiology, studying the action of ultraviolet and ionizing radiation on microorganisms. Research in the field of radiation Microbiology are aimed at: 1) mechanisms of biological action of ultraviolet and ionizing radiation on microorganisms; 2) the use of radiation as a factor causing hereditary variability or the death of the bacteria.
Microorganisms are widely used object radiobiological experiments to study General regularities of action of radiation on the cell. In this area of radiation Microbiology directly linked with radiobiology (see). Radiation Microbiology decides however important practical tasks with economic importance, such as the use of radiation as a factor of transformation of nature organisms with the purpose of obtaining large outputs of biologically valuable substances (antibiotics, vitamins, hormones, amino acids). For sterilizing the effect of radiation is based method of cold sterilization (see), which often has advantages before sterilization of heat or antiseptics, and sometimes the only possible one.
The action of ionizing radiation on heredity was first discovered in experiments with microorganisms. In 1925, A. Nadson, and S. Filippov found that under the influence of x-ray radiation in microorganisms cause change steadfastly continued in subsequent generations (mutations). This observation has begun development of a new branch of knowledge - radiation genetics (see). Radiation Microbiology takes into account opened by this science patterns, in particular the fact that in a certain range of doses of radiation, the number of mutant forms is increased proportionally to the dose. Using ionizing radiation of natural frequency of the mutation process may be increased tenfold. Of course, increased output of a variety of hereditary modified variants affecting various inherited characteristics of microorganisms. That is why the mere exposure without further breeding cannot serve as a way of getting changed in the desired direction forms of microorganisms. Exposure only to result in microbial populations greater number of options with hereditary changes. Following selection on the basis of interest allows faster and with greater likelihood of success is to select necessary for those or other needs an option. So, for example, selection of strains-producers of penicillin Penicillium chrysogenum with prior exposure to x-ray and ultraviolet radiation allowed the American microbiologists to select variants with productivity more than 100 times greater than the production of penicillin parent strain. The use of mutants induced by neutrons, x - rays and ultraviolet radiation or chemical mutagens, in 15-30 times has increased the productivity of strains-producers of streptomycin, chlortetracycline, oxytetracycline. The works on radiation breeding other important in production against strains of microorganisms (vaccine, toxigenic, producers of amino acids and so on).
Problems of radiation Microbiology related to the use of the sterilizing effects of radiation, primarily related to the definition of radiation doses and radiation terms providing for the death of microorganisms. Bactericidal action of x-rays was known already at the end of the last century. However, practical use of ionizing radiation for the purpose of sterilization has only been possible in recent years due to the creation of powerful irradiators, in particular gamma irradiators, charged with radioactive cobalt. Modern gamma irradiators provide the opportunity for a huge dose of radiation in a short time and in large volumes of irradiated object. The necessity in creation of large power plants for the purpose of sterilization is a relatively high radioresistance of microorganisms. If for mammals lethal dose range of 400-1000 glad that inactivation of microbes depending on irradiation conditions only occurs with doses of the order of hundreds of thousands or millions glad.
Bactericidal action of ionizing radiation depends on a number of factors. Drying of microorganisms increases the radioresistance. A similar effect has reduced partial pressure of oxygen in the irradiated object, the decrease of temperature during irradiation, as well as the conditions created after exposure. In cases of exposure microbial culture of microorganism sensitivity varies depending on the cycle of the development of culture.
Different organisms have different radioresistance. So, for example, to achieve the sterilizing effect of the irradiation of solids etiology of bacteria (Bact. coli, Proteus vulgaris need irradiation in doses 100 000-500 000 happy. For the inactivation of spores spore-forming microorganisms need large doses - 1 000-2 500 500 000 happy.- Even more resistant viruses: sterilizing effect occurs only when irradiation in doses of 3 000 000 - 5 000 000 happy.