河流中抗生素污染及其管理

抗生素污染已经引起越来越多研究者的重视,但国内外的报道主要集中在抗生素残留的调查及残留物的转移和消除过程,有关抗生素对环境、生物及生态系统影响的研究很少。在实际情况中,由于抗生素被大量使用或使用不恰当,造成环境抗生素污染事故屡屡发生。本文综述了近年来国内外有关河流环境中抗生素污染研究的最新进展,提出了河流环境中抗生素污染的解决办法,对抗生素污染的研究方向进行了展望。     

近岸海域抗生素污染状况的研究进展

抗生素是海洋环境中的一类新型污染物,由于其使用量的逐年增大导致污染程度的加深,对人类健康和海洋生态环境构成威胁.为了弄清近岸海域中抗生素的分布特点,减少残留抗生素对海洋环境的污染,保障海洋生态系统的健康发展,通过查阅资料,实际调查,样品比对等方法,研究了近岸海域抗生素的污染来源及分布特征,探讨了抗生素对海洋生态环境的影响,并针对我国海洋现状提出了今后的研究重点,主要包括以下四方面:(1)开展敏感区域污染状况调查,探讨抗生素污染物进入海洋的主要路径,开发降解去除抗生素的方法.(2)建立和完善低浓度抗生素含量分析方法,掌握海洋环境中抗生素的污染水平,弄清海洋环境中抗生素的时空分布特点.(3)研究不同种类抗生素在海洋环境中的行为归宿.(4)开展海洋生态环境风险评估,分析抗生素及其降解产物的毒性.     

喹诺酮类抗生素在水环境中降解和吸附影响因素

抗生素污染会对水生态系统和人类健康产生风险,其在水环境中的主要迁移转化途径为吸附和降解,环境条件直接影响抗生素在水环境中的残留水平.为进一步确定抗生素在水环境中降解和吸附行为的影响因素,以喹诺酮类抗生素为例,在建立高效液相色谱-质谱法测试喹诺酮类抗生素的基础上,通过单一变量实验研究介质粒径、水环境pH和初始浓度对氧氟沙星和加替沙星降解和吸附行为的影响.结果 表明:在颗粒粒径0.25～2 mm,介质粒径越小,抗生素降解效率越低,在入渗能力和透气性较好的粗颗粒介质中,更有利于抗生素的降解和吸附.氧氟沙星和加替沙星降解率最高的pH分别为7.38和7.73,天然水pH范围利于抗生素的降解自净;在细砂介质中的吸附过程符合Freundlich方程,初始浓度对细砂介质中抗生素去除率的影响较为显著,随着初始浓度的增加而增大,在初始浓度为60μg/L达到峰值,继而缓慢降低,过高或过低的初始浓度均不利于抗生素的吸附和降解.     

抗生素在水中的污染及其对环境的危害

本文介绍了抗生素在水中的污染及抗生素对环境的危害，针对抗生素对环境的危害指出了今后的研究方向。     

2019年水环境安全热点回眸

 水是生命之源，水环境安全是人类生存与发展的必要条件。2019年，水污染控制、地表水生态环境、地下水环境保护等领域科技进展显著。本文围绕水资源、水生态、水环境，介绍了2019年生活污水与工业废水污染控制、地表水生态流量与氮排放限值、地下水资源保护与污染防控等方面的全球科技研究热点及亮点工作，回顾了中国水环境安全的2019年。     

乳化液泄漏事故应急终止后水环境恢复跟踪监测与研究

环境污染事故中,水污染事故占有很大比例,目前水污染事故应急终止后开展水环境恢复的有关研究尚少。该文通过对水环境污染事故响应终止后对水环境进行全方面监测,探讨环境污染事故水环境动态变化趋势,分析事故污染扩展影响途径,评估水环境恢复状况。结果表明：①水环境污染事故应急终止后,其水环境影响主要扩展至河流沉积物、水生生物：②受污染沉积物将缓慢释放污染物,造成局部污染物浓度高于周边水环境质量指标;③水生态环境中初级生产力较易得到恢复,大型底栖生物恢复能力较差。     

探讨屋顶绿化对美化改善城市环境的作用

我国从上个世纪60年代研究屋顶绿化的建造技术。随着我国经济水平不断的提高,城市环境不断地恶劣,从而引起的一系列问题,政府和民众开始意识到城市生态环境建设的紧迫性。屋顶绿化的出现,不但了丰富城市的立体空间色彩、仰视景观和俯视景观。还改善了城市建设过程中的由于生态环境的恶化,出现的＂热岛效应＂、＂温室效应＂、大气环境和水环境被严重污染等诸多环境问题。     

城市道路建设项目环境污染及防治措施

分析了城市道路建设项目的污染源及污染物,根据城市道路建设项目不同时期(施工期、运营期)对环境要素(环境空气、水环境、声环境、生态环境等)产生的影响程度和范围,提出了有针对性的防治措施,为城市道路建设项目的污染防治及环境管理工作提供支撑。     

东昌湖流域生态补水管理模式探讨

目前国际上已将湖泊水环境研究的重心转向湖泊流域生态系统管理,即从流域尺度对湖泊进行污染治理、生态恢复以及生态系统管理,实现湖泊流域内社会经济协调与湖泊生态系统健康的可持续发展。笔者在对东昌湖流域生态补水管理概念界定的基础上,提出了东昌湖流域生态补水管理概念模式、东昌湖流域社会经济协调发展优化模式、东昌湖水质水量保障和生态环境改善的环境管理体系。它涵盖了流域管理、水环境管理和生态系统管理的思想和内容。     

SPAC系统中氮平衡及其模拟模型

环境中氮污染对人类生活和生产影响很大。该文研究了氮肥在SPAC系统的分布情况及氮素平衡问题，建立了氮肥在SPAC系统的综合数学模型。该模型为排水条件下减少氮肥流失措施提供一定的依据，可有效提高氮肥利用率并减少其对环境的影响，尤其是减少其对水环境的污染。     

A transposon, Tn732, encoding gentamicin/tobramycin resistance.

Gentamicin and tobramycin are important antibiotics in the treatment of hospital infections because of their activity against a wide range of bacterial genera. With their increasing use, bacteria resistant to these drugs have appeared, the resistance being frequently plasmid determined. The resistance genes determine various enzymes that modify and inactivate the drugs and there is association between particular gentamicin/tobramycin resistance genes and plasmids of particular groups, implying that acquisition of such a gene by any plasmid is a rare event. We now report the identification of a transposon or 'jumping gene' encoding the gentamicin/tobramycin adenylylating enzyme, ANT(2"), on a plasmid of incompatiblity group FII (IncFII).     

养殖环境病原菌以及超级细菌气溶胶的发生与传播的监测

为了观察和评估养殖环境耐药细菌气溶胶的形成与扩散,采用Andersen-6级空气样品收集器在养鸡场鸡舍环境舍内、外(到下风方向800 m)收集空气样品;与此同时,采集鸡只粪便样品。对样品分离的大肠杆菌(E.coli)进行药物敏感性测试。结果显示,各个地点分离的E.coli对利福平和青霉素完全耐药,但他们对妥布霉素、庆大霉素敏感;有不同数量的菌株对氟哌酸、链霉素、头孢哌酮、氯霉素、复合磺胺和四环素有不同程度的耐药性。采用多重PCR方法,分别对从鸡、猪、牛舍(共21个)及其环境中分离到的480株大肠杆菌,进行了5种毒素基因即STa,STb,LTa,Stx1和Stx2/Stx2e的检测。结果表明,分离株都携带有一定数量的毒素基因,很多携带2种或2种以上。通过对11个动物舍(鸡、猪、牛、兔)空气和粪便样品分离的426株肠球菌对四环素类(TetM)、氨基糖甙类抗生素及万古霉素VanA和VanB主要耐药基因的检测表明,14.55%的细菌对β-内酰胺酶耐药;分离株都存在不同程度的对四环素类抗生素的耐药性;共检测出31株肠球菌携带vanA和vanB耐药基因;绝大多数肠球菌携带氨基糖苷修饰酶(AME)基因的一种或几种。     

Transposition of an antibiotic resistance element in mycobacteria

Bacterial resistance to antibiotics is often plasmid-mediated and the associated resistance genes encoded by transposable elements. Mycobacteria, including the human pathogens Mycobacterium tuberculosis and M. leprae, are resistant to many antibiotics, and their cell-surface structure is believed to be largely responsible for the wide range of resistance phenotypes. Antibiotic-resistance plasmids have so far not been implicated in resistance of mycobacteria to antibiotics. Nevertheless, antibiotic-modifying activities such as aminoglycoside acetyltransferases and phosphotransferases have been detected in fast-growing species. beta-lactamases have also been found in most fast- and slow-growing mycobacteria. To date no mycobacterial antibiotic-resistance genes have been isolated and characterized. We now report the isolation, cloning and sequencing of a genetic region responsible for resistance to sulphonamides in M. fortuitum. This region also contains an open reading frame homologous to one present in Tn1696 (member of the Tn21 family) which encodes a site-specific integrase. The mycobacterial resistance element is flanked by repeated sequences of 880 base pairs similar to the insertion elements of the IS6 family found in Gram+ and Gram- bacteria. The insertion element is shown to transpose to different sites in the chromosome of a related fast-growing species, M. smegmatis. The characterization of this element should permit transposon mutagenesis in the analysis of mycobacterial virulence and related problems.     

Antibiotic resistance is ancient

The discovery of antibiotics more than 70 years ago initiated a period of drug innovation and implementation in human and animal health and agriculture. These discoveries were tempered in all cases by the emergence of resistant microbes. This history has been interpreted to mean that antibiotic resistance in pathogenic bacteria is a modern phenomenon; this view is reinforced by the fact that collections of microbes that predate the antibiotic era are highly susceptible to antibiotics. Here we report targeted metagenomic analyses of rigorously authenticated ancient DNA from 30,000-year-old Beringian permafrost sediments and the identification of a highly diverse collection of genes encoding resistance to β-lactam, tetracycline and glycopeptide antibiotics. Structure and function studies on the complete vancomycin resistance element VanA confirmed its similarity to modern variants. These results show conclusively that antibiotic resistance is a natural phenomenon that predates the modern selective pressure of clinical antibiotic use.     

Gene expression in Pseudomonas aeruginosa biofilms.

Bacteria often adopt a sessile biofilm lifestyle that is resistant to antimicrobial treatment. Opportunistic pathogenic bacteria like Pseudomonas aeruginosa can develop persistent infections. To gain insights into the differences between free-living P. aeruginosa cells and those in biofilms, and into the mechanisms underlying the resistance of biofilms to antibiotics, we used DNA microarrays. Here we show that, despite the striking differences in lifestyles, only about 1% of genes showed differential expression in the two growth modes; about 0.5% of genes were activated and about 0.5% were repressed in biofilms. Some of the regulated genes are known to affect antibiotic sensitivity of free-living P. aeruginosa. Exposure of biofilms to high levels of the antibiotic tobramycin caused differential expression of 20 genes. We propose that this response is critical for the development of biofilm resistance to tobramycin. Our results show that gene expression in biofilm cells is similar to that in free-living cells but there are a small number of significant differences. Our identification of biofilm-regulated genes points to mechanisms of biofilm resistance to antibiotics.     

湘江四环素及抗性基因含量特征及其季节变化

采用高效液相色谱质谱法分析了湘江长沙河段水体及底泥中4种常见四环素类抗生素的含量特征及其季节变化,并采用实时荧光定量PCR研究了该水域相应的5种代表性抗生素抗性基因(tet A,tet C,tet G,tet M和tet X)的存在及丰度.结果表明,水体中四环素类抗生素的质量浓度均值在16.23~496.73ng·L-1之间,底泥中四环素类抗生素的质量分数为347.77~3 829.75ng·kg-1,易受季节变化影响.5种目标抗性基因在所有样品中均有检出,其中tet A和tet C的绝对拷贝数及相对丰度较高,为湘江长沙河段的优势抗性基因.相关性分析表明:冬季水体中的tet A和tet C含量与底泥中的含量显著相关,几种目标抗生素与抗性基因之间并不存在明显线性关系.     

DNA cloning in Streptomyces: resistance genes from antibiotic-producing species

The biochemical and morphological differentiation of actinomycetes makes them academically and economically interesting. Their secondary metabolites provide the majority of medically and agriculturally important antibiotics (streptomycete genes may also be the primary source of clinically important antibiotic resistance); their complex morphological developmental cycle involves a series of changes from vegetative mycelial growth to spore formation. Recombinant DNA technology would add a powerful new dimension to the analysis of these various aspects of actinomycete biology and would also facilitate the development of industrial strains with increased antibiotic yield, or capable of making new antibiotics. For most of these purposes, cloning of genes within and between actinomycetes is required to study the expression of particular genes in genetic backgrounds defined by mutations of the characters under study. To achieve this, we have now developed a method for molecular cloning involving the transfer of genes between unrelated streptomycetes.     

微塑料的老化及其对水环境中抗生素的吸附行为研究进展

微塑料(microplastics, MPs)和抗生素作为新兴污染物,经常在水环境中能被同时检测到,并且水环境中的抗生素也经常在MPs表面被发现。MPs可以通过表面吸附和迁移,吸收、聚集并携带水环境中的各类有机污染物而受到广泛关注。与原始MPs相比,老化后的MPs因粒径变小、比表面积增大,从而吸附位点增多,而具有更强的吸附能力。主要从MPs的环境老化方式、老化后MPs对水环境中各类抗生素的吸附行为展开了综述,总结了老化MPs的老化方法及吸附抗生素的影响因素及吸附机理,并对MPs老化问题及对抗生素的吸附影响提出展望。     

抗生素与肠道菌群关系研究进展

 从抗生素与肠道菌群的关系出发,在抗生素角度,概述了抗生素对肠道菌群构成、肠道定植抗力、菌群类别及代谢活动的影响,综述了抗生素通过调节肠道菌群恢复肠-脑轴、肠-肝轴稳态,延缓非感染性疾病的研究进展。在肠道菌群角度,简述了肠道菌群在抗生素耐药基因储存传播、新型抗生素发现过程中的特别作用。     

SOS response promotes horizontal dissemination of antibiotic resistance genes

Mobile genetic elements have a crucial role in spreading antibiotic resistance genes among bacterial populations. Environmental and genetic factors that regulate conjugative transfer of antibiotic resistance genes in bacterial populations are largely unknown. Integrating conjugative elements (ICEs) are a diverse group of mobile elements that are transferred by means of cell-cell contact and integrate into the chromosome of the new host. SXT is a approximately 100-kilobase ICE derived from Vibrio cholerae that encodes genes that confer resistance to chloramphenicol, sulphamethoxazole, trimethoprim and streptomycin. SXT-related elements were not detected in V. cholerae before 1993 but are now present in almost all clinical V. cholerae isolates from Asia. ICEs related to SXT are also present in several other bacterial species and encode a variety of antibiotic and heavy metal resistance genes. Here we show that SetR, an SXT encoded repressor, represses the expression of activators of SXT transfer. The 'SOS response' to DNA damage alleviates this repression, increasing the expression of genes necessary for SXT transfer and hence the frequency of transfer. SOS is induced by a variety of environmental factors and antibiotics, for example ciprofloxacin, and we show that ciprofloxacin induces SXT transfer as well. Thus, we present a mechanism by which therapeutic agents can promote the spread of antibiotic resistance genes.