Screening And Identification Of Mercury Resistant Fungi And Study Of Its Application Potential

In recent years,heavy metal pollution of soil is becoming more and more pronounced,and it has become a severe problem to human health and social development.However,remediation techniques are also developing rapidly,especially the development of bioremediation technologies,which are providing an efficient,eco-friendly way to solve this problem.The study aims at isolating microbes from polluted soil,and identifying the strains,furthermore,determining the growth conditions,fungi metalcharacteristics,pathogenic bacteria antagonism and the effects of plant growth.In this research,we hope to provide scientific evidences for theirapplication.Methods of isolation of Hg²⁺-resistant fungal: using fluid PDA medium for enrichment culturing,screening by Hg²⁺ plate medium and then using higher concentration Hg²⁺ plate medium for subculture;The identification of fungiusingrational morphological methods and modern molecular ITSrDNA sequencing method;In the study of growth conditions,usingmycelia dry weight to evaluate the growth of fungi;Fungi metal-resistanceevaluated by two variables,fungi growth inhibition rate and medial lethal concentration?EC50?.The method in biosorption characteristics was that;firstly,mycelium ballsput into heavy metal ion solution of knownconcentrations.Few hours later,the remaining concentrations were analyzed,heavy metal adsorption efficiency and adsorption quantity were calculated,then fitted the adsorption process with function model;In forest pathogen antagonism experiment,plate confrontation method is used to investigate the inhibition of Trichoderma virens and Penicillium oxalicumagainst Cryphonectria parasitic,Colletotrichum gloeosporioides,Neocosmospora rubicola Fusariumsolani and Fusarium Oxysporum;Finally we used hydroponics to test the growthpromoting effect of Trichoderma virens,Penicillium oxalicum and Biochemical Fulvic Acid?BFA?in wheat,which was under heavy metal stress.Separating six strains fungi with 300mg/L Hg²⁺ plate,named from lys2015f1 to lys2015f6.Species identification results showed that they belong toTrichoderma virens,Acremonium falciforme,Cochliobolus setariae,Gibberella fujikuroi,Penicillium oxalicum,and Aspergillus flavus;Culture conditionsforTrichoderma virens and Penicillium oxalicum showed that the optimum temperature is 28?,optimumculture medium pH is 7,and the optimum cultivate length of time is 96 h.;In metal-resistance experiments,the Trichoderma virens' s EC50 value of Hg²⁺,Zn²⁺,Cu²⁺,Pb²⁺were 158.07,464.02,229.33,209.59mg/L,respectively;Penicillium oxalicumwere 580.47,572.88,231.85,2284.01mg/L,respectively.From EC50 value we putTrichoderma virens in the order of heavy metal tolerance level: Zn²⁺>Cu²⁺>Pb²⁺>Hg²⁺,tolerance level order of Penicillium oxalicum is Pb²⁺>Hg²⁺>Zn²⁺>Cu²⁺.The adsorption process was more fitting pseudo-second-order kinetic model,form k2 value we could get the adsorption rate of two strains,they have the same order in those metal ions Pb²⁺>Hg²⁺>Cu²⁺> Zn²⁺;In the experiment of antagonism,Trichoderma virens inhibition rates against Cryphonectria parasitic,Colletotrichum gloeosporioides,Neocosmospora rubicola Fusariumsolani and Fusarium Oxysporum were 100.00%,35.96%,37.40% and 35.96%,respectively.AndPenicillium oxalicum inhibition rates for them were 100.00%,73.68%,63.41%,60.78%,respectively;In wheat experiment,according to the results of the germination rate,penicillium oxalateshowed the best effect,the effect of BFA take second place;In leaf elongation experiment,under Hg²⁺,Cu²⁺,Zn²⁺stress,Trichoderma viride's promoting effect was better.Under Pb²⁺stress,Penicillium oxalicum and BFA promotion better.In root elongation experiment,under the stress of high concentration of Hg²⁺,Trichoderma viride showed better promoting effect.When Zn²⁺ concentration was 80 mg/L,Penicillium oxalicum and BFA promoting effect was the best.The results showed that two strains hadstrong abilities to heavy metal tolerance and adsorption,biological control and plant growth.In conclusion,two strains in repairing heavy metal contaminated soil have great applicationpotential.