Response of antibiotic and heavy metal resistance genes to the co-occurrence of gadolinium and sulfamethoxazole in activated sludge systems

With the increasing use of antibiotics and rare earth elements(REE)during the coronavirus disease(COVID-19)pandemic,the co-occurrence of sulfamethoxazole(SMX)and gadolinium(Gd)has increased in wastewater treatment plants(WWTPs).However,the effects of SMX and Gd exposure on the transmission of antibiotic resistance genes(ARGs)and heavy metal resistance genes(MRGs)remain unknown.This study investigated the impacts of SMX and Gd on the fate of ARGs and MRGs in an activated sludge system.The diversity and relative abundance of ARGs,MRGs,and mobile genetic elements(MGEs)were detected by metagenomic sequencing.The results revealed an increased abundance of ARGs but a decreased abundance of MRGs under the joint effect of SMX and Gd.In addition,Gd alone exerted adverse effects on the proliferation and spread of ARGs and MRGs.However,SMX alone resulted in an increase in the diversity of ARGs and MRGs and promoted the growth of Pseudomonas,Thauera,and Streptomyces in the activated sludge system.Interestingly,a positive correlation was observed between most ARGs and MGEs.These findings provide comprehensive insights into the effects of co-occurring REEs and antibiotics on the fate of ARGs,MRGs,and MGEs,providing evidence to assist in controlling the spread and proliferation of ARGs and MRGs in activated sludge systems.

Genomic analyses of metal resistance genes in three plant growth promoting bacteria of legume plants in Northwest mine tailings, China

To better understand the diversity of metal resistance genetic determinant from microbes that survived at metal tailings in northwest of China, a highly elevated level of heavy metal containing region, genomic analyses was conducted using genome sequence of three native metal-resistant plant growth promoting bacteria（PGPB）. It shows that： Mesorhizobium amorphae CCNWGS0123 contains metal transporters from P-type ATPase, CDF（Cation Diffusion Facilitator）, Hup E/Ure J and CHR（chromate ion transporter） family involved in copper, zinc, nickel as well as chromate resistance and homeostasis. Meanwhile, the putative Cop A/Cue O system is expected to mediate copper resistance in Sinorhizobium meliloti CCNWSX0020 while Znt A transporter, assisted with putative Czc D, determines zinc tolerance in Agrobacterium tumefaciens CCNWGS0286. The greenhouse experiment provides the consistent evidence of the plant growth promoting effects of these microbes on their hosts by nitrogen fixation and/or indoleacetic acid（IAA） secretion,indicating a potential in-site phytoremediation usage in the mining tailing regions of China.

Metagenomic analysis on resistance genes in water and microplastics from a mariculture system

Microplastics existing widely in different matrices have been regarded as a reservoir for emerging contaminants.Mariculture systems have been observed to host microplastics and antibiotic resistance genes(ARGs).However,more information on proliferation of ARGs and metal resistance genes(MRGs)in mariculture system at the presence of microplastics is needed.This study used metagenomic analysis to investigate the distribution of ARGs and MRGs in water and microplastics of a typical mariculture pond.Total 18 types including 174 subtypes of ARGs were detected with the total relative abundances of 1.22/1.25 copies per 16S rRNA copy for microplastics/water.Chloramphenicol resistance genes were the dominant ARGs with the abundance of 0.35/0.42 copies per 16S rRNA copy for microplastics/water.Intergron intI1 was dominant gene among 6 detected mobile genetic elements(MGEs)with the abundance of 75.46/68.70 copies per 16S rRNA copy for water/microplastics.Total 9 types including 46 subtypes of MRGs were detected with total abundance of 5.02×10^(2)/6.39×10^(2)copies per 16S rRNA copy for water/microplastics while genes resistant to copper and iron served as the dominant MRGs.Proteobacteria,Bacteroidetes,and Actinobacteria accounted for 84.2%/89.5%of total microbial community in microplastics/water.ARGs with relatively high abundance were significantly positively related to major genera,MGEs,and MRGs.Microplastics in mariculture system could enrich most of MRGs and some ARGs to serve as potential reservoir for these pollutants.The findings of this study will provide important information on resistance gene pollution at presence of microplastics in the mariculture system for further proposing suitable strategy of environmental management.

Genomic characterization of multidrug-resistant extraintestinal pathogenic Escherichia coli isolated from grain culture soils

Multidrug-resistant(MDR)Escherichia coli,mainly extraintestinal pathogenic E.coli(ExPEC),has been widely reported in infections worldwide.In agricultural soils,manure is a hotspot for the dissemination of antimicrobial resistance genes(ARGs)and pathogenic bacteria;however,MDR bacteria have also been reported in soils with no history of manure use.In addition,cross-resistance and co-resistance have been described as responsible for the metal-driven selection of bacteria resistant to antimicrobials.Therefore,the aim of this study was to analyze three MDR E.coli isolates obtained from Brazilian grain culture soil samples with no history of manure use by whole-genome sequencing.The MDR E.coli isolates were recovered from soils from corn and coffee fields,and presented resistance toβ-lactams,quinolones,aminoglycosides,tetracyclines,sulphonamides,and dihydrofolate reductase inhibitor.Resistome analysis showed ARGs to several antimicrobials(i.e.,β-lactams,tetracyclines,aminoglycosides,sulphonamides,trimethoprim,phenicols,fosfomycin,and macrolides)as well as several metal resistance genes and antibacterial biocide resistance genes.In addition,known mutations in quinolone-resistance-determining regions of GyrA(Ser83Leu and Asp87Asn),ParE(Ser458Thr),and ParC(Ser80Ile)were also detected.Virulome analysis showed the presence of virulence genes(lpfA,mcmA,gad,mchF,iroN,cma,and iss)associated with ExPEC.Multidrug-resistant ExPEC isolates were assigned to phylogenetic group B1.The presence of MDR B1-ExPEC in soil samples shows the ability of these isolates to survive in soils.This study reports for the first time some sequence types(i.e.,ST345,ST448,and ST1146)of MDR E.coli in Brazilian soils.Therefore,these findings contribute to the monitoring of antimicrobial resistance and surveillance studies based on whole-genome sequencing worldwide.