Isolation And Identification Of New Strains And Screening Of Arsenic And Cadmium Resistant Strains

With the development of various underground resources and the progress and development of modern industrial society,the resulting soil pollution problems have become increasingly serious,among which the pollution of arsenic and cadmium is particularly prominent.There are many kinds of microorganisms,their numbers are complicated,and they are widely distributed.They are precious biological resources.However,only 1%of bacteria can be obtained through cultivable methods.The development of microbial resources has unparalleled potential and value.In modern agriculture,the use of microorganisms to treat heavy metal pollution in the soil has increasingly become a new direction for farmland pollution treatment.In this thesis,firstly,bacteria were isolated and identified from arsenic-contaminated soil(34 mg/kg)from Longkou Town,Honghu City,Jingzhou City,Hubei Province,in order to screen new strains and develop new strain resources.In addition,arsenic-resistant strains were isolated from the soil of a pig farm in Shayang,Hubei Province to explore the possibility of treating arsenic and cadmium compound pollution.The following conclusions were reached:(1)A ZY74~T strain with a 16S r RNA gene sequence similarity of 97.72%was isolated from arsenic-contaminated soil(34 mg/kg)in Longkou Town,Honghu City,Jingzhou City,Hubei Province.It is suspected to be a new species,based on its genotype and morphology,Growth characteristics,physiology and biochemistry,chemical classification,and genome analysis to identify ZY74~Tand determine its taxonomic status.The results show that ZY74~Thas the typical characteristics of chitin,and at the same time has its own uniqueness,and the average nucleotide identity(ANI)and digital DNA-DNA hybridization(d DDH)results between ZY74~T and the reference strain genome are both Lower than the threshold of prokaryotic species classification(95%-96%,70%).(2)An arsenic-resistant strain ZY8 was isolated from the soil of a pig farm in Shayang,Hubei Province,and analyzed from several aspects such as morphology,partial growth characteristics,minimum inhibitory concentration of heavy metals(MIC),and genome analysis.Preliminary analysis showed that the ZY8 strain has multiple heavy metal resistance,and there are corresponding heavy metal resistance genes in the genome.The arsenic oxidation ability,cadmium removal ability of the strain,and the arsenic oxidation and cadmium removal under the combined presence of arsenic and cadmium were tested under laboratory conditions,and it was found that the bacteria has good arsenic oxidation and cadmium removal ability.Summarizing the above results,this study isolated and identified a new strain of ZY74~T,named Chitinophaga lutea,model strain ZY74~T(=CCTCC AB2018369T=KCTC 72039T),which enriched the strain resources and provided reference and theoretical basis for subsequent research.At the same time,a strain ZY8 with stable arsenic oxidation and cadmium removal phenotype was screened.It not only has the potential to deal with arsenic and cadmium compound pollution,but its characteristics of resistance to multiple heavy metals indicate that this strain also has the value of dealing with multiple compound pollution.