| The antimicrobial property of nano zinc oxide has been paid more and more attentions.However,there are still some problems in the research of zinc oxide.On the one hand,the antimicrobial performance of zinc oxide is mainly concentrated on the study of bacteria,while the studies on the fungi are less.On the other hand,studies about the antimicrobial mechanisms of zinc oxide still have no unified conclusions.In addition,some studies have reported that morphology plays a great influence on antibacterial property of zinc oxide.In view of the above situations,the self-made nano zinc oxide with different morphologies were used as antifungal agent to study their antifungal property againt different species of fungi so as to screen out the nano zinc oxide with broad antifungal activity selecting the inhibition rate as the screening criteria.Based on those,we analyzed the antifungal mechanisms of zinc oxide through five aspects: antifungal property of nano zinc oxide under sunlight and dark conditions,imitating antifungal property of zinc ion which is dissolved from nano zinc oxide,observation of interaction between zinc oxide and fungus,detections of physiological and biochemical indexes of fungi treated by zinc oxide and RNA-sequencing of fungus.Those results could provide the theoretical basis and reference for the study of antifungal properties and mechanisms of zinc oxide.The main research contents and conclusions are as follows:(1)Three methods including emulsion method,direct precipitation method and microemulsion method were used to prepare three kinds of nano zinc oxide with different morphologies.The inhibition rate was used to compare the antifungal properties of three zinc oxide against three species of fungi(Penicillium,Mucor and Myxomycete)so as to screen out the nano zinc oxide with broad antifungal property.The results showed that morphologies of spherical shaped,flake shaped and flower shaped nano zinc oxide were prepared by three methods respectively.Three zinc oxides all showed obviously inhibitory effect on three kinds of fungi.The inhibition rate of three zinc oxide are flower shaped > flake shaped > spherical shaped.Results aboved showed that the nano zinc oxide with broad antifungal activity was successfully screened out.(2)Using flower shaped nano zinc oxide as Antifungal agents,Penicillium as the experimental object,we analyzed the antifungal mechanisms of nano zinc oxide from four aspects: antifungal property of nano zinc oxide against Penicillium under sunlight and dark conditions,imitating antifungal property of zinc ion which is dissolved from nano zinc oxide against Penicillium,observation of interaction between zinc oxide and Penicillium,detections of physiological and biochemical indexes of Penicillium treated by zinc oxide.The results showed that zinc oxide both showed antifungal property against Penicillium under daylight irradiation and dark conditions and the antifungal effect has no difference,showing that the photocatalytic antimicroal mechanism of nano zinc oxide is not the only antimicrobial mechanism.The growth of Penicillium was inhibited when zinc ion concentration was higher than 3.571 mmol/L,while the concentration of zinc ion dissolved from nano zinc oxide can not be up to 3.571 mmol/L,which demonstrated that the zinc ion dissolution from zinc oxide was not the main mechanism in this study.Scanning electron microscopy results showed that zinc oxide is adsorbed on the surface of mycelium of Penicillium.The morphology of mycelium was changed,and even some mycelia were fractured.At the same time,the intracellular SOD and CAT activity of Penicillium treated by zinc oxide were both increased obviously and MDA content was increased.It could be drawn the conclusion that nano zinc oxide inhibits the growth of fungi by directly attaching to the surface of fungi,which caused oxidative stress on fungi destroying the cellular physiological activity.(3)RNA-sequencing of Penicillium treated by zinc oxide(experimental group)and Penicillium without treatment by zinc oxide(control group)obtained 31 837 number of unigenes of high quality.14 062 and 5 006 number of unigenes were annotated to GO and KEGG database respectively.Then the genes related to the inhibition of growth of Penicillium were screen out.The results indicated that genes associated with oxidative stress in experimental group of Penicillium showed significant up-regulation in gene expression.In addition,genes related to the complete composition of membrane,zinc ion binding,transmembrane transport,oxidative phosphorylation were found showing significant up or down-regulation in gene expression.Above results demonstrated that the antifungal effect of nano zinc oxide against Penicillium has close relationship with those genes.It was further proved that the nano zinc oxide could inhibit the growth of Penicillium by oxidative stress induced by the interaction between zinc oxide and Penicillium.Dissolved zinc ion from nano zinc oxide could promote the antifungal activity of zinc oxide through entering the cell.In addition,some other genes expressed in the experimental group were also found showing up or down-regulation in gene expression to some extent,which revealed that they may play an important role in the process of nano zinc oxide against penicillium,therefore deserving to further study. |
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