Antimicrobial Activities Of Intestinal Trichoderma Brevicompactum In Pheretima Tschiliensis And Its Adsorption Of Heavy Metals

Long-term overuse of chemical pesticides is prone to produce resistance to diseases and insect pests,causing environmental pollution and damaging beneficial colony in soil.The harmful substances in pesticides can even harm human health by means of biological chain concentration.Heavy metals are extremely toxic to the environment and biological health.In recent years,industrial operations such as metallurgy,steel,atomic installation have aggravated soil heavy metal pollution.Microbial remediation is one of a method to solve the soil heavy metal pollution problem.It is of great significance for agricultural production to screen microbial strains with biocontrol ability and heavy metal adsorption capacity.In this paper,a Trichoderma with biocontrol ability and heavy metal adsorption was isolated from the intestinal tract of Pheretima.The results are as follows:1.Twenty Trichoderma strains were isolated from the intestinal tract of Pheretima tschiliensis.Trichoderma strain QYCD-6 has a good role of antagonism to Fusarium oxysporum f.sp.cucumerinum(FOC)with the inhibition rate of 80.6%and also has good inhibition activites against other plant pathogenic fungus with the inhibition rate of above 60%by petri dish confrontation bioassay.The results of pot experiment showed that the protective effect of QYCD-6 against FOC was 82%.QYCD-6 was identified as Trichoderma brevicompactum.In addition,QYCD-6 has a certain growth-promoting effect on cucumber plants,and can significantly improve the plant height,root length,dry weight and fresh weight of cucumber.The prevention and treatment mechanism of QYCD-6 against FOC was preliminarily discussed:the microscopic observation showed that QYCD-6 and FOC mycelia could entangle each other and attach to the growth of FOC mycelia,and puncture FOC mycelia led to fold fracture and even inactivation of the mycelia.The main mechanism of QYCD-6 anti-FOC action was determined to be heavy parasitism,competition and antagonism.Compared with the blank control(cucumber seedlings without treatment),the root SOD and CAT activities of cucumber seedlings treated with QYCD-6.2.QYCD-6 has good tolerance and adsorption to a variety of heavy metals.QYCD-6 has good tolerance to Pb(?).Minimum inhibitory concentration(MIC)of different heavy metals[Cu(?),Cr(?),Cd(?),Pb(?)and Zn(?)]for T.brevicompactum ranged 250-1600 mg L-1 on PD media with highest MIC recorded for Pb(?)followed by Zn(?).MIC of heavy metal[Cu(?),Cr(VI),Cd(?)and Zn(?)]was relatively low with ranged 150-200 mg L-1 on composite media,respectivelly.When treated QYCD-6 with 50 mg L-1 heavy metals for 120 h.The adsorption rates of heavy metals in QYCD-6 strain were:Pb(?)(97.5%),Cu(?)(64.5%),Cr(?)(24.8%),Cd(16.8%),Zn(?)(4.6%);The adsorption effects of Trichoderma QYCD-6 to different heavy metal concentrations(30,50,100 mg L-1)were tested.The results showed that except for Pb(?),the biomass of QYCD-6 decreased with the increaseing initial concentration of heavy metals.The biomass decreased most in Cd(?)followed by Multi metal,Cr(?),Cu(?)and Zn(?);when the concentration of heavy metal is 100 mg L-1,the amount of heavy metals absorbed by QYCD-6 strain is Zn(?),Pb(?),Cr(?),Cu(?),Cd(?)and Multi metal;Adsorption capacity of QYCD-6 was largely effected by temperature and optimal temp is 28?.The influence of pH is small,and the optimum pH is 9.FTIR analysis indicated the involvement of different surface functional groups in biosorption of different metals,such as-OH,-NH2,C-C,C=C,C-O-C,-P=O,C-O-P and other groups play an important role.While cellular changes in fungus was reflected by TEM analysis,which proved removal of heavy metals via sorption and accumulation processes.In conclusion,T.brevicompactum QYCD-6 can inhibit the growth of pathogenic fungi and has good biocontrol potential.T.brevicompactum QYCD-6 has certain tolerance and adsorption ability to a variety of heavy metals,and has a good application prospect.