Effects Of Heavy Metals And Oxytetracycline On Microbial Communities And Antibiotic Resistance Genes

Heavy metal pollution,heavy metal and antibiotic compound pollution have become global problems.These pollutants have a great negative impact on soil properties,production constraints and environmental functions,and may even pose a serious threat to human health.Microorganisms in soil are considered the most sensitive biological indicators of soil quality and are the most active part of soil organic components and ecosystems,and play an important role in promoting soil quality and plant health.In this paper,the distribution of microorganisms in soil contaminated by heavy metals and the main mechanism affecting microbial changes were studied firstly.Then,the effects of oxytetracycline(OTC)and cadmium(Cd)on antibiotic resistance gene(ARGs),microbial community structure in soil and lettuce were studied under laboratory conditions.The aims of this study were to explore the possible effects of the single or compound contamination of heavy metals and antibiotics on microbial communities and human health.The main results of the study are as follows:(1)To improve the understanding of bacterial community in heavy metals contaminated soils,we studied the effects of environmental factors on the bacterial community structure in contaminated fields located in Shaanxi Province of China.Our results showed that microbial community structure varied among sites,and it was significantly affected by soil environmental factors such as pH,soil organic matter(OM),Cd,Pb and Zn.In addition,Spearman's rank-order correlation indicated heavy metal sensitive(Ralstonia,Gemmatimona,Rhodanobacter and Mizugakiibacter)and tolerant(unidentified-Nitrospiraceae,Blastocatella and unidentifiedAcidobacteria)microbial groups.(2)In order to analyze the effects of antibiotics and heavy metals on soil microbial ecosystems and humans,we studied the effects of OTC and Cd on ARGs,microbial community in soil and lettuce by pot experiment with OTC and Cd as pollutant.The results showed that OTC and Cd had significant effect on the microbial community,ARGs and OTC changed the abundance of ARGs and intI1 in the soil,which may facilitate the spread of ARGs in the environment,heavy metals reducd the amount of OTC content in the soil,but increased the migration of ARGs to plant leaves,which may pose a significant risk to human health.Bentonite(BT)not only reduced the accumulation of OTC in the soil,but also reducesthe abundance of ARGs.BT is expected to become a good material for soil antibiotics and heavy metal repair.