Influence Of Irradiation On Yangtze River Microbial Population Structure And Ecological Functions

In recent years,the construction of inland nuclear power stations has become an important agenda in the energy strategy of China.However,once the leakage accidents happen,the radioactive pollution will affect all creatures in the surrounding environment.So far,studies related to the impact from irradiation on non-human species mainly focus on animals and plants,and few involve the microbial populations.However,when the surviving environment changes,microbes can make corresponding changes through relevant mechanism,which reflects the impact from irradiation on the environment from the biological perspective.Thus,exploring the correlation between microbial population's changes and functional damage and irradiation intensity,and understanding the influence from irradiation on micro-ecosystem are very important.This paper takes the the Yangtze river water and sediment as research objects,using two methods,the dilute coating and high throughput sequencing,to explore the impact from irradiation on the structure of microbial population in the environment.Obtaining pure microbes through streaking and conducting traditional physiological and biochemical experiment and molecular biology identification,we can determine the species' information.And then,through measuring the change of microbial ecological function indexes before and after the irradiation,we can understand the effects of irradiation on the ecological functions of microbes.The results are as follows:(1)In the water samples,irradiation intensity of 2Gy doesn't have huge impact on cultivable microbes.When the irradiation intensity is 20 and 200 Gy,the number of microbes declines 35.59% and 71.06%,and species abundance increases 4 and 3.In each strain,Flavobacterium suffers from the biggest impact from irradiation,whose proportion of the sample declines 28.98% and death rate is 86.05%.Bacillus has the strongest tolerance towards irradiation,whose proportion increases 15.72%.Strain d(Flavobacterium nitratireducens strain N1)is most sensitive to the irradiation,whose proportion falls by 24.25% and survival rate is only 11.58%.(2)In the sediment sample,the irradiation intensity of 20 and 200 Gy can make the number of cultivable microbes fall by 28.10% and 44.63%.After the 200 Gy irradiation,the number of strains from the cultivation is 6 less than that in the control group.In each strain,Bacillus has the strongest tolerance towards irradiation,whose proportion in the sample increases 37.14%.By contrast,Flavobacterium experiences the biggest impact from irradiation,whose proportion in the sample falls by 26.1%.(3)Results from the high throughout sequencing indicate that the proportions of five kinds of microbes in the sample,which are Crenarchaeota,Euryarchaeota,Chloroflexi,Spirochaetes and Firmicutes,increase with the increase of irradiation intensity,showing their strong tolerance towards irradiation.The proportions of Bacteroidetes and Proteobacteria in the sample decrease with the increase of irradiation intensity.Among them,the decrease of Proteobacteria's proportion reaches 6.8%,suggesting a comparable high sensitivity from Proteobacteria to irradiation.The proportions of three kinds of dominant strains separated from traditional methods have the consistent changing trend with the results from high throughput sequencing in the sample.(4)Irradiation can lead to the decline of dehydrogenase and phosphatase' activity in the microbes.When the microbe itself has a high enzyme activity,the decline of enzyme activity is larger.Compared with the impact on the dehydrogenase activity,the impact from irradiation on phosphatase activity is more significant.In contrast to the enzyme activity,irradiation will increase microbes' oxygen-consumption respiration rate.