Research On The Occurrence And Application Potential Of Bacteria-Bacteriophage Cooperation Under Arsenic Exposure

Bacteriophages(Phages)are the most abundant biological entities on earth.They can be divided into lysogenic phage(the lysogenic phage that enters the lysogenic cycle called prophage)and lytic phage according to whether the phage can insert its DNA into the host genome and enter the lysogenic cycle.Among them,lysogenic phage can change the genome composition and expression of its host,and it may enhance the host's fitness to facilitate to adverse environments.However,the role of lysogenic phage helps their host to against arsenic in the arsenic-contaminated soil is completely unknown.Under long-drawn arsenic stress,microorganisms have evolved a complete anti-arsenic system,but it is still unknown whether lysogenic phages are involved in the transduction of microbial anti-arsenic systems among different microorganisms.In this study,a porous material that can be attached by microorganisms was prepared in the laboratory.After incubation in an arsenic solution with the same arsenic concentration as the sampling site,it was used as an attachment matrix for arsenic-resistant microorganisms in arsenic-contaminated soil.In order to avoid microbial structural variation,the arsenic-resistant microorganisms were eluted from the sampling beads immediately,and used mitomycin C(MC)to induce the prophage in the arsenic-resistant microorganism genome.We have determined typical arsenic resistance genes ars C(arsenic detoxification reduction gene)and ars M(arsenic methylation gene)in the phage's DNA of soil arsenic-resistant microorganisms from Shimen site by PCR amplification and sequencing verification.In order to understand whether phage-mediated horizontal gene transfer is involved in the exchange of arsenic-resistant genes among environmental microbial communities,we detected the abundance of arsenic-resistance genes in the bacterial genome(normalized to each bacterial 16 S DNA)by quantitative PCR)and the abundance of arsenic-resistance genes in the genome of the induced lysogenic phage(normalized to each phages).The regression analysis showed that the abundance of ars C and ars M in lysogenic phage was positively correlated with the abundance of ars C and ars M in the soil bacterial genome.In order to investigate the non-indigenous transduction ability of lysogenic phage and to investigate the potential of using phage to treat arsenic pollution,we conducted a microcosmic experiment.The experimental results show that inoculation of the live phage(is close to the amount of arsenic in natural soil)that contains the arsenic-resistance gene caused the total abundance of ars C and ars M in the microcosm and the relative abundance of ars C and ars M in the propagated phage,which indicates that the lysogenic phage we extracted has the ability of non-indigenous infection.The proliferation of arsenic-resistant genes also triggered changes in arsenic species in the microcosm.In short,the content of As(III)increased significantly.In order to understand the real changes of arsenic ecotoxicity in the microcosm,we designed the soil earthworm avoidance experiment.The experimental results showed that the arsenic toxicity of soil increased significantly after phage inoculation.This study reported that there is a typical microbial arsenic-resistant gene in the prophage in the genome of arsenic-resistant microorganisms,and showed that lysogenic phage is involved in the horizontal gene transfer of arsenic-resistant genes for the first time.Microcosmic experiments have shown that these bacteriophages have the ability to ectopically infect,which triggers an increase in the toxicity of arsenic in the soil.This article lays the foundation for understanding the role of bacteriophages in the global arsenic cycle.