| Silver nanoparticles(AgNPs)own many excellent properties especially the broad-spectrum antimicrobial properties due to the special structure.It was used in many industries,as well as brought risks to soil environment.In this study,an incubation experiment was conducted to investigate the effects of AgNPs on soil respiration,enzyme activities and microbial community functional diversity in comparison to silver nitrate(AgNO3)and graphene.The findings will provide the fundamental evidence to estimate the environmental risks caused by AgNP for future research;and the growth,cell structure and transcriptome of Fusarium solani which was a soil-borne fungus were investigated to explore responses of AgNPs to F.solani.The main results were obtained as follows:1.There was a significant inhibition of soil respiratory rates by AgNPs.The inhibitory effect of AgNPs on soil respiration was greater than that of AgNO3.But there was no significant effect of graphene on soil respiration.2.The numbers of incubated soil bacteria,fungi and actinomycetes were inhibited significantly by 100 mg·kg-1、150 mg·kg-1 AgNPs and AgNO3 in soil.However,the graphene had no significant impact on the number of soil microorganisms at low concentration(10 mg·kg-1,100 mg·kg-1 soil),but could stimulate the soil bacteria and fungi at high concentration(1000 mg·kg-1 soil).3.Further investigation showed that the AgNPs pronouncedly inhibited the soil urease and dehydrogenase activities,but had no effect on soil catalase and alkaline phosphatase activities.And the inhibitory effect of AgNPs was greater than AgNO3 on soil urease and dehydrogenase activity.They were pronouncedly inhibited by 10 mg·kg-1AgNPs and 100 mg·kg-1 AgNO3.Soil alkaline phosphatase activity was significantly inhibited by the presence of graphene.4.The negative effects of AgNPs on the soil microbial community,Shannon,Simpson and McIntosh diversity indices were more obvious than that of AgNO3,and both of them had a significant effect on it at concentration of 150 mg·kg-1.Meanwhile,the functional diversity of soil microbial community was also reduced by graphene.5.There was a significant inhibition of F.solani growth when incubated with AgNPs in a concentration dependent manner.The growth of F.solani was completely inhibited with 10 mg·L-1 AgNPs,and the EC50 value was 3.6 mg·L-1.The cell wall,cell membrane and cell organelle of F.solani were destroyed by AgNPs,and suspected silver particles were observed in the cell membrane.6.Based on the analysis of F.solani transcriptome after AgNPs treatment,23791 Unigenes were obtained,and 862,867,774 differentially expressed genes were found at 6 h,12 h and 24 h,respectively(P < 0.05).Results of GO enrichment analysis showed that differentially expressed genes were mainly distributed in protein processing,oxidoreductase activity,catabolism,cell composition acting on carbon-nitrogen hydrolase activity,structural molecular activity,translation,external packaging structure,RNA binding and Precursor metabolites and energy generation categories.Results of KEGG pathway analysis showed that the genes of F.solani in transcription,translation,folding,sorting and degradation,carbohydrate metabolism,energy metabolism,signal transduction and signal molecule and interaction pathway expressed different significantly.7.By further comparison of the differentially expressed genes between control and AgNPs treatment,they were concentrated in energy and substrate metabolism,signal transduction and genetic information pathways,including TCA cycle,sulfur metabolism,antioxidant enzyme activity,heat shock protein,protein synthesis and decomposition,DNA repair process.So we deduced that F.solani cells were killed by AgNPs through disturbing the energy metabolism,producing ROS,causing protein or even DNA damage. |
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