Organochlorine compounds and polycyclic aromatic hydrocarbons in surface sediment from Baiyangdian Lake,North China:Concentrations,sources profiles and potential risk

Organochlorine pesticides （OCPs）, polychlorinated biphenyls （PCBs）, and polycyclic aromatic hydrocarbons （PAHs） were determined in nineteen surface sediment samples collected from Baiyangdian Lake and its inflowing river （Fuhe River） in North China. Total concentrations of OCPs, PCBs and PAHs in sediments ranged from 5.4 to 707.6 ng]g, 2.3 to 197.8 ng/g, and 101.3 to 6360.5 ng]g, respectively. The levels of contaminants in Fuhe River were significantly higher than those in Baiyandian Lake. For hexachlorocyclohexane （HCHs） and dichlorodiphenytrich/oroethanes （DDTs）, α-HCH and p,p＇-DDT were predominant isomers; while for PCBs, PCB 28/31, PCB 40/103, PCB 60, PCB 101, and PCB 118 were predominant congeners. Possible sources derived from historical usage for OCPs and incomplete combustion fuel, wood, and coal and exhaustion of boats or cars for PAHs. Risk assessment of sediment indicated that sediments in Fuhe River were likely to pose potential biological adverse impact.

Brominated flame retardants in surface sediment from Western Guangdong,South China:Occurrence,distribution and toxicity in Caenorhabditis elegans

Sediment is the ultimate sink of environmental pollutants.A total of 128 surface sediment sampleswere collected from8 rivers and 3 reservoirs in Maoming City,Guangdong Province.This study assessed the content and distribution of brominated flame retardants in sediments.The acute toxicity effects of tetrabromobisphenol A(TBBPA)and hexabromocyclododecane(HBCDs)in sediments were evaluated using Caenorhabditis elegans as model organisms.The concentration of TBBPA in sediments ranged from not detected(ND)to 12.59μg/kg andwas mainly distributed in the central area,whichwas affected by the emission of TBBPA from residential and factory.The concentration of HBCDs ranged from ND to 6.31μg/kg,and the diastereoisomer distribution was consistent,showing a trend close to the South China Sea.The composition pattern of HBCDs in the surface sediments from rivers were 41.73%-62.33%,7.89%-25.54%,and 18.76%-40.65%forα-,β-,andγ-HBCD,respectively,and in the sediments from reservoirs were 26.15%-45.52%,7.44%-19.23%,and 47.04%-61.89%forα-,β-,andγ-HBCD,respectively.When the sum of concentrations of TBBPA and HBCD in sediments were above high levels,reactive oxygen species in nematodes significantly increased,resulting in an oxidative stress response.Intestinal permeabilitywas also enhanced,causing intestinal damage.In addition,in terms of this study,TBBPA had a greater impact on biotoxicity compared to HBCDs,and more attention should be paid to the toxic effects of the river ecosystem organisms in Maoming City,Guangdong Province.This study can complement the pollution database in the study area and provide basic data for pollution control.

Characteristics of the multiple replicon plasmid IncX1-X1 in multidrug-resistant Escherichia coli from Malayan pangolin(Manis javanica)

Potential zoonotic pathogens may be transmitted from wildlife to humans through the illegal wild meat trade,which has become a pressing issue.However,research on the antimicrobial resistance genes(ARGs)of Malayan pangolin(Manis javanica)intestinal bacteria is limited.Here,multidrug-resistant Escherichia coli M172-1(ST354)isolated from Malayan pangolin feces in 2019 was found to be resistant to 13 antibiotics.BGWAS analysis revealed 4 plas-mids,namely,pM172-1.1,pM172-1.2,pM172-1.3,and pM172-1.4,in the isolate.The pM172-1.2,pM172-1.3,and pM172-1.4 plasmids carried ARGs,namely,IncHI2-HI2A,IncX1-X1,and IncX1,respectively.pM172-1.3 and pM172-1.4 contained intact IntI1 integrons(Is26/IntI1/arr2/cmlA5/blaOXA-10/ant(3′′)-IIA/dfrA14/Is26).No-tably,pM172-1.3 resulted from the fusion of 2 pM172-1.4 copies and carried many more ARGs.In addition to pM172-1.3 from the same host,other drug-resistant bacteria(E.coli M159-1(ST48),E.coli S171-1(ST206),and Klebsiella pneumoniae S174-1(ST2354))in the same Malayan pangolin fecal samples also carried 3 plasmids with 100%gene coverage of pM172-1.4 and 99.98%identity.Therefore,ARGs in IncX1 might spread in the intestinalflora of Malayan pangolin and between species via the illegal food chain,posing a potential threat to public health and safety.

克雷伯氏菌属(Klebsiella)细菌比较基因组学分析揭示多复制子抗性质粒介导广泛的抗性基因传播

【目的】研究克雷伯氏菌与多复制子抗性质粒间的关系,分析细菌携带多复制子质粒对抗生素环境的响应机制。【方法】以2018-2020年分离的56株不同来源克雷伯氏菌(Klebsiella sp.)分离株为研究对象,利用微量肉汤稀释法评估其多重耐药表型,对分离菌株进行全基因组测序(WGS),通过细菌全基因组关联分析(BGWAS)技术和比较基因组学方法深入解析多复制子抗性质粒形成的机制。【结果】耐药表型分析发现野生动物来源的菌株具有更广的耐药谱系,总体Klebsiella sp.对氨苄西林表现出很高的耐药率(80.36%),尤其是马来穿山甲来源菌株对头孢类抗生素高度耐受,同时对氯霉素、左氧氟沙星和复方新诺明等药物耐受,基因组分析发现这些菌株携带了抗性质粒和更多的抗生素抗性基因。进一步对69个质粒序列分析,发现有28个质粒为多复制子质粒,主要携带bla_(CTX-M-15)、bla_(CTX-M-14)、bla_(CTX-M-55)、bla_(OXA-1)和bla_(TEM-1)等β-内酰胺酶基因。细菌携带质粒类型分析认为Klebsiella pneumoniae可能是多复制子质粒的重要宿主,质粒骨架与结构分析发现多复制子质粒多由2个或2个以上单个质粒融合而成,携带此类质粒的菌株不仅获得了更广的耐药表型,而且在全球传播扩散分布逐年增加,因此产生对抗生素环境更强的适应性。【结论】多重耐药性细菌呈现的表型与携带的多复制子质粒有关,相比较下多复制子质粒比非多复制子质粒有更强的抗性基因携带能力,或许是细菌在强大的抗生素压力下产生的重要响应机制。本研究对于未来探索细菌抗性基因的传播扩散机制具有重要意义。

Distribution of polybrominated diphenyl ethers and decabromodiphenylethane in surface sediments from Fuhe River and Baiyangdian Lake,North China

Nineteen surface sediment samples collected from Baiyangdian Lake and its inflowing river （Fuhe River） in North China were analyzed for polybrominated diphenyl ethers （PBDEs） and decabromodiphenylethane （DBDPE）. The concentrations of PBDEs and DBDPE in sediments ranged from 5.5 to 300.7 ng/g dry weight （dw） and 1.1 to 68.2 ng/g dw, respectively. Their levels in sediments in Fuhe River were significantly higher than those in Balyandian Lake. Compared to data from other regions, the PBDE levels in surface sediments from Baiyangdian Lake and Fuhe River were in the medium to lower range. Among the PBDE congeners, BDE209 was predominant, with contributions to the total PBDEs ranging from 79.4% to 97.3% in sediment samples. For the lowly brominated congeners （tri- to hepta-BDE）, BDE47 and BDE99 were the most abundant, which contributed 52.1% and 44.1% to the sum of tri- to hepta-BDEs in the sediments from Baiyangdian Lake and Fuhe River, respectively. The compositional patterns of PBDEs in Baiyangdian Lake sediments indicated that technical deca-BDE mixture was the major pollutant sources with a minor contribution of penta-BDE mixture. The present study suggested that the importance of Fuhe River as a possibly potential sources of PBDEs contamination in Baiyangdian Lake.

Characterization and Fine Mapping of a Novel Rice Narrow Leaf Mutant nal9

A narrow leaf mutant was isolated from transgenic rice （Oryza sativa L.） lines carrying a T-DNA insertion. The mutant is characterized by narrow leaves during its whole growth period, and was named nal9 （narrow leaf 9）. The mutant also has other phenotypes, such as light green leaves at the seedling stage, reduced plant height, a small panicle and increased tillering. Genetic analysis revealed that the mutation is controlled by a single recessive gene. A hygromycin resistance assay showed that the mutation was not caused by T-DNA insertion, so a map-based cloning strategy was employed to isolate the nal9 gene. The mutant individuals from the F2 generations of a cross between the nal9mutant and Longtepu were used for mapping. With 24 F2 mutants, the nal9 gene was preliminarily mapped near the marker RM156 on the chromosome 3. New INDEL markers were then designed based on the sequence differences between japonica and indica at the region near RM156. The nal9 gene was finally located in a 69.3 kb region between the markers V239B and V239G within BAC OJ1212_C05 by chromosome walking. Sequence and expression analysis showed that an ATP-dependent CIp protease proteolytic subunit gene （CIpP） was most likely to be the nal9 gene. Furthermore, the nal9 mutation was rescued by transformation of the CIpP cDNA driven by the 35S promoter. Accordingly, the CIpP gene was identified as the NAL9 gene. Our results provide a basis for functional studies of NAL9 in future work.

Multidrug-resistant Proteus mirabilis isolates carrying blaOXA-1 and blaNDM-1 from wildlife in China:increasing public health risk

The emergence of multidrug resistance(MDR)in Proteus mirabilis clinical isolates is a growing public health concern and has serious implications for wildlife.What is the role of wildlife has been become one of the hot issues in disseminating antimicrobial resistance.Here,54 P.mirabilis isolates from 12 different species were identified.Among them,25 isolates were determined to be MDR by profile of antimicrobial susceptibility;10 MDR P.mirabilis isolates were subjected to comparative genomic analysis by whole genome sequencing.Comprehensive analysis showed that chromosome of P.mirabilis isolates mainly carries multidrug-resistance complex elements harboring resistance to carbapenem genes blaOXA-1,blaNDM-1,and blaTEM-1.Class I integron is the insertion hotspot of IS26;it can be inserted into type I integron at different sites,thus forming a variety of multiple drug resistance decision sites.At the same time,Tn21,Tn7,and SXT/R391 mobile elements cause widespread spread of these drug resistance genes.In conclusion,P.mirabilis isolates from wildlife showed higher resistance to commonly used clinic drugs comparing to those from human.Therefore,wild animals carrying MDR clinical isolates should be paid attention to by the public health.

Profiling kidney microRNAs from juvenile grass carp(Ctenopharyngodon idella) after 56 days of oral exposure to decabromodiphenyl ethane

Grass carp（Ctenopharyngodon idella） is one of the most important species in China.Decabromodiphenyl ethane（DBDPE） is a brominated flame retardant that has been used widely in industry, and has been observed to accumulate in the tissues of fish from South China. Evidence has shown that DBDPE is toxic to aquatic animals, but the molecular response has been unclear. MicroRNAs（miRNAs） are small noncoding and negative regulatory RNAs that are 20–24 nucleotides in length, which are involved in a wide range of biological processes. We took advantage of deep-sequencing techniques to accurately and comprehensively profile the kidney mi RNA expression of grass carp after 8 weeks of oral exposure to DBDPE. After mapping sequencing data to the genome and Expressed Sequence Tags（ESTs） of grass carp, we identified 493 miRNAs in the sequenced grass carp samples, which included 51 new miRNAs. The results indicated that 5 miRNAs were significantly down-regulated and 36 miRNAs were significantly up-regulated（FDR 〈 0.001,1.5-fold change） after DBDPE exposure. Real-time quantitative PCR（RT-qPCR） was performed on 4 miRNAs from the two samples, and the sequencing and RT-qPCR data were consistent. This study provides the first comprehensive identification of grass carp miRNAs, and the first expression analysis of grass carp miRNAs following DBDPE exposure.The results indicated that miRNAs have potential for use as biomarkers.