Effects Of Alizarin On Antibiotic Resistance And Community Of Microorganisms In Lake Wate

At present,little is known about the fugitive characteristics of antibiotic resistance genes（ARGs）,the structure of microbial communities,the alteration of population functions and the determination of potential host bacteria of ARGs in the aqueous environment under the exposure of alizarin.Therefore,in this study,a lab-scale lake water simulation system was established by adding 10%inhibition concentration(IC₁₀)or half inhibition concentration(IC₅₀)antibiotics to investigate the effects of exogenous antibiotics on lake water.In addition,another simulation system was also established by adding alizarin or the combination of alizarin and IC₁₀ antibiotics with greater impact on microbial resistance to observe the effect of drug treatment on water samples.Real-time fluorescence quantitative PCR（q PCR）technology,high-throughput sequencing and metagenomic analyses were used to analyze target genes assignment,diversity and composition of microbial communities,population function and the correlation between ARGs and genera.The aim was to further explore the effects of alizarin on antibiotic resistance and microbial communities in lake water,and to provide data support for future ecological risk assessment and scientific control.The qPCR results showed that the introduction of exogenous antibiotics promoted the production and transmission of ARGs and int I1.The disparity in antibiotic concentrations between IC₁₀ and IC₅₀ conferred distinct persistence characteristics to ARGs,with the highest absolute abundance observed in the IC₁₀ concentration antibiotic treatment group.16S r RNA gene analysis indicated that exogenous antibiotics reduced microbial diversity,altered the composition of the main community,and this was directly related to changes in antibiotic concentration and time.Among the 21 and 27 phyla detected in the tetracycline and ciprofloxacin treatment groups,respectively,the average relative abundance of Proteobacteria was the highest.Among the 395 and 491 genera detected in the tetracycline and ciprofloxacin treatment groups,respectively,some genera were significantly positively correlated with ARGs or int I1 and were identified as potential host bacteria.Differences in antibiotic types led to diversity in the host bacterial structure of ARGs and int I1 in water samples.Exposure to alizarin increased the abundance of 16S r RNA genes,ARGs,and int I1 in water samples,and the co-exposure of alizarin and antibiotics most significantly promoted population growth and induced ARGs.Metagenomic analysis revealed that alizarin reduced microbial species diversity and,compared to antibiotics,more significantly changed the microbial community structure at the phylum and genus levels,resulting in changes in population function.After 30 days of treatment with alizarin and tetracycline,a total of 20 phyla and 219 genera were detected in the water samples.Similarly,after 30 days of treatment with alizarin and ciprofloxacin,a total of 20 phyla and 363 genera were detected in the water samples.The genera Sphingopyxis,uncultured＿bacterium＿f＿Xanthobacteraceae,and Aeromonas,along with 10 other dominant bacterial genera,showed a significant positive correlation with one or more antibiotic resistance genes（ARGs）,indicating their potential role as hosts for ARGs.